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Features
Compatible with MCS-51TM Products 8K Bytes of In-System Reprogrammable Downloadable Flash Memory
SPI Serial Interface for Program Downloading Endurance: 1,000 Write/Erase Cycles 2K Bytes EEPROM Endurance: 100,000 Write/Erase Cycles 4.0V to 6V Operating Range Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 256 x 8-bit Internal RAM 32 Programmable I/O Lines Three 16-bit Timer/Counters Nine Interrupt Sources Programmable UART Serial Channel SPI Serial Interface Low Power Idle and Power Down Modes Interrupt Recovery From Power Down Programmable Watchdog Timer Dual Data Pointer Power Off Flag

8-Bit Microcontroller with 8K Bytes Flash AT89S8252

Description
The AT89S8252 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of Downloadable Flash programmable and erasable read only memory and 2K bytes of EEPROM. The device is manufactured using Atmel's high density nonvolatile memory technology and is compatible with the industry standard 80C51 instruction set and pinout. The on-chip Downloadable Flash allows the program memory to be reprogrammed in-system through an SPI serial interface or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Downloadable Flash on a monolithic chip, the Atmel AT89S8252 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The AT89S8252 provides the following standard features: 8K bytes of Downloadable Flash, 2K bytes of EEPROM, 256 bytes of RAM, 32 I/O lines, programmable watchdog timer, two Data Pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S8252 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset. The Downloadable Flash can be changed a single byte at a time and is accessible through the SPI serial interface. Holding RESET active forces the SPI bus into a serial programming interface and allows the program memory to be written to or read from unless Lock Bit 2 has been activated.

0401D-A12/97

4-105

Pin Configurations
PDIP
(T2) P1.0 (T2 EX) P1.1 P1.2 P1.3 (SS) P1.4 (MOSI) P1.5 (MISO) P1.6 (SCK) P1.7 RST (RXD) P3.0 (TXD) P3.1 (INT0) P3.2 (INT1) P3.3 (T0) P3.4 (T1) P3.5 (WR) P3.6 (RD) P3.7 XTAL2 XTAL1 GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 VCC P0.0 (AD0) P0.1 (AD1) P0.2 (AD2) P0.3 (AD3) P0.4 (AD4) P0.5 (AD5) P0.6 (AD6) P0.7 (AD7) EA/VPP ALE/PROG PSEN P2.7 (A15) P2.6 (A14) P2.5 (A13) P2.4 (A12) P2.3 (A11) P2.2 (A10) P2.1 (A9) P2.0 (A8)

PLCC
P1.4 (SS) P1.3 P1.2 P1.1 (T2 EX) P1.0 (T2) NC VCC P0.0 (AD0) P0.1 (AD1) P0.2 (AD2) P0.3 (AD3) P0.4 (AD4) P0.5 (AD5) P0.6 (AD6) P0.7 (AD7) EA/VPP NC ALE/PROG PSEN P2.7 (A15) P2.6 (A14) P2.5 (A13)

PQFP/TQFP
P1.4 (SS) P1.3 P1.2 P1.1 (T2 EX) P1.0 (T2) NC VCC P0.0 (AD0) P0.1 (AD1) P0.2 (AD2) P0.3 (AD3)

44 43 42 41 40 39 38 37 36 35 34

(MOSI) P1.5 (MISO) P1.6 (SCK) P1.7 RST (RXD) P3.0 NC (TXD) P3.1 (INT0) P3.2 (INT1) P3.3 (T0) P3.4 (T1) P3.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

33 32 31 30 29 28 27 26 25 24 23

Pin Description
VCC Supply voltage. GND Ground. Port 0 Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs. Port 0 can also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode, P0 has internal pullups.

(WR) P3.6 (RD) P3.7 XTAL2 XTAL1 GND GND (A8) P2.0 (A9) P2.1 (A10) P2.2 (A11) P2.3 (A12) P2.4

Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pullups are required during program verification. Port 1 Port 1 is an 8-bit bidirectional I/O port with internal pullups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Some Port 1 pins provide additional functions. P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively.

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(WR) P3.6 (RD) P3.7 XTAL2 XTAL1 GND NC (A8) P2.0 (A9) P2.1 (A10) P2.2 (A11) P2.3 (A12) P2.4

18 19 20 21 22 23 24 25 26 27 28

(MOSI) P1.5 (MISO) P1.6 (SCK) P1.7 RST (RXD) P3.0 NC (TXD) P3.1 (INT0) P3.2 (INT1) P3.3 (T0) P3.4 (T1) P3.5

7 8 9 10 11 12 13 14 15 16 17

6 5 4 3 2 1 44 43 42 41 40

39 38 37 36 35 34 33 32 31 30 29

P0.4 (AD4) P0.5 (AD5) P0.6 (AD6) P0.7 (AD7) EA/VPP NC ALE/PROG PSEN P2.7 (A15) P2.6 (A14) P2.5 (A13)

AT89S8252
Block Diagram
P0.0 - P0.7 P2.0 - P2.7

VCC PORT 0 DRIVERS GND PORT 2 DRIVERS

EEPROM

RAM ADDR. REGISTER

RAM

PORT 0 LATCH

PORT 2 LATCH

FLASH

B REGISTER

ACC

STACK POINTER

PROGRAM ADDRESS REGISTER

BUFFER TMP2 TMP1

ALU INTERRUPT, SERIAL PORT, AND TIMER BLOCKS

PC INCREMENTER

PSW

PROGRAM COUNTER

PSEN ALE/PROG EA / VPP RST WATCH DOG PORT 3 LATCH PROGRAM LOGIC TIMING AND CONTROL INSTRUCTION REGISTER DPTR

PORT 1 LATCH

SPI PORT

OSC PORT 3 DRIVERS PORT 1 DRIVERS

P3.0 - P3.7

P1.0 - P1.7

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Furthermore, P1.4, P1.5, P1.6, and P1.7 can be configured as the SPI slave port select, data input/output and shift clock input/output pins as shown in the following table.
Port Pin P1.0 P1.1 P1.4 P1.5 P1.6 P1.7 Alternate Functions T2 (external count input to Timer/Counter 2), clock-out T2EX (Timer/Counter 2 capture/reload trigger and direction control) SS (Slave port select input) MOSI (Master data output, slave data input pin for SPI channel) MISO (Master data input, slave data output pin for SPI channel) SCK (Master clock output, slave clock input pin for SPI channel)

Port Pin P3.0 P3.1 P3.2 P3.3 P3.4 P3.5 P3.6 P3.7

Alternate Functions RXD (serial input port) TXD (serial output port) INT0 (external interrupt 0) INT1 (external interrupt 1) T0 (timer 0 external input) T1 (timer 1 external input) WR (external data memory write strobe) RD (external data memory read strobe)

RST Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. ALE/PROG Address Latch Enable is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode. PSEN Program Store Enable is the read strobe to external program memory. When the AT89S8252 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. EA/VPP External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming when 12volt programming is selected.

Port 1 also receives the low-order address bytes during Flash programming and verification. Port 2 Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. Port 3 Port 3 is an 8 bit bidirectional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also serves the functions of various special features of the AT89S8252, as shown in the following table. Port 3 also receives some control signals for Flash programming and verification.

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XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit. XTAL2 Output from the inverting oscillator amplifier.

Special Function Registers
A map of the on-chip memory area called the Special Function Register (SFR) space is shown in Table 1. Note that not all of the addresses are occupied, and unoccupied addresses may not be implemented on the chip. Read accesses to these addresses will in general return random data, and write accesses will have an indeterminate effect.

Table 1. AT89S8252 SFR Map and Reset Values
0F8H 0F0H 0E8H 0E0H 0D8H 0D0H 0C8H 0C0H 0B8H 0B0H 0A8H 0A0H 98H 90H 88H 80H IP XX000000 P3 11111111 IE 0X000000 P2 11111111 SCON 00000000 P1 11111111 TCON 00000000 P0 11111111 TMOD 00000000 SP 00000111 TL0 00000000 DP0L 00000000 TL1 00000000 DP0H 00000000 TH0 00000000 DP1L 00000000 TH1 00000000 DP1H 00000000 SPDR XXXXXXXX PCON 0XXX0000 SBUF XXXXXXXX WMCON 00000010 SPSR 00XXXXXX PSW 00000000 T2CON 00000000 T2MOD XXXXXX00 RCAP2L 00000000 RCAP2H 00000000 TL2 00000000 SPCR 000001XX TH2 00000000 ACC 00000000 B 00000000 0FFH 0F7H 0EFH 0E7H 0DFH 0D7H 0CFH 0C7H 0BFH 0B7H 0AFH 0A7H 9FH 97H 8FH 87H

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User software should not write 1s to these unlisted locations, since they may be used in future products to invoke new features. In that case, the reset or inactive values of the new bits will always be 0. Timer 2 Registers Control and status bits are contained in registers T2CON (shown in Table 2) and T2MOD (shown in Table 9) for Timer 2. The register pair (RCAP2H, RCAP2L) are the Capture/Reload registers for Timer 2 in 16 bit capture mode or 16-bit auto-reload mode. Watchdog and Memory Control Register The WMCON register contains control bits for the Watchdog Timer (shown in Table 3). The EEMEN and EEMWE bits are used to select the 2K bytes on-chip EEPROM, and to enable byte-write. The DPS bit selects one of two DPTR registers available. Table 2. T2CON--Timer/Counter 2 Control Register
T2CON Address = 0C8H Bit Addressable TF2 Bit Symbol TF2 EXF2 7 Function EXF2 6 RCLK 5 TCLK 4

SPI Registers Control and status bits for the Serial Peripheral Interface are contained in registers SPCR (shown in Table 4) and SPSR (shown in Table 5). The SPI data bits are contained in the SPDR register. Writing the SPI data register during serial data transfer sets the Write Collision bit, WCOL, in the SPSR register. The SPDR is double buffered for writing and the values in SPDR are not changed by Reset. Interrupt Registers The global interrupt enable bit and the individual interrupt enable bits are in the IE register. In addition, the individual interrupt enable bit for the SPI is in the SPCR register. Two priorities can be set for each of the six interrupt sources in the IP register.

Reset Value = 0000 0000B

EXEN2 3

TR2 2

C/T2 1

CP/RL2 0

Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set when either RCLK = 1 or TCLK = 1. Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX and EXEN2 = 1. When Timer 2 interrupt is enabled, EXF2 = 1 will cause the CPU to vector to the Timer 2 interrupt routine. EXF2 must be cleared by software. EXF2 does not cause an interrupt in up/down counter mode (DCEN = 1). Receive clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock in serial port Modes 1 and 3. RCLK = 0 causes Timer 1 overflows to be used for the receive clock. Transmit clock enable. When set, causes the serial port to use Timer 2 overflow pulses for its transmit clock in serial port Modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock. Timer 2 external enable. When set, allows a capture or reload to occur as a result of a negative transition on T2EX if Timer 2 is not being used to clock the serial port. EXEN2 = 0 causes Timer 2 to ignore events at T2EX. Start/Stop control for Timer 2. TR2 = 1 starts the timer. Timer or counter select for Timer 2. C/T2 = 0 for timer function. C/T2 = 1 for external event counter (falling edge triggered). Capture/Reload select. CP/RL2 = 1 causes captures to occur on negative transitions at T2EX if EXEN2 = 1. CP/RL2 = 0 causes automatic reloads to occur when Timer 2 overflows or negative transitions occur at T2EX when EXEN2 = 1. When either RCLK or TCLK = 1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow.

RCLK TCLK EXEN2 TR2 C/T2 CP/RL2

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Dual Data Pointer Registers To facilitate accessing both internal EEPROM and external data memory, two banks of 16 bit Data Pointer Registers are provided: DP0 at SFR address locations 82H-83H and DP1 at 84H-85H. Bit DPS = 0 in SFR WMCON selects DP0 and DPS = 1 selects DP1. The user should always initialize the DPS bit to the Table 3. WMCON--Watchdog and Memory Control Register
WMCON Address = 96H Reset Value = 0000 0010B

appropriate value before accessing the respective Data Pointer Register. Power Off Flag The Power Off Flag (POF) is located at bit_4 (PCON.4) in the PCON SFR. POF is set to "1" during power up. It can be set and reset under software control and is not affected by RESET.

PS2 Bit Symbol PS2 PS1 PS0 EEMWE EEMEN DPS WDTRST RDY/BSY 7 Function

PS1 6

PS0 5

EEMWE 4

EEMEN 3

DPS 2

WDTRST 1

WDTEN 0

Prescaler Bits for the Watchdog Timer. When all three bits are set to "0", the watchdog timer has a nominal period of 16 ms. When all three bits are set to "1", the nominal period is 2048 ms. EEPROM Data Memory Write Enable Bit. Set this bit to "1" before initiating byte write to on-chip EEPROM with the MOVX instruction. User software should set this bit to "0" after EEPROM write is completed. Internal EEPROM Access Enable. When EEMEN = 1, the MOVX instruction with DPTR will access on-chip EEPROM instead of external data memory. When EEMEN = 0, MOVX with DPTR accesses external data memory. Data Pointer Register Select. DPS = 0 selects the first bank of Data Pointer Register, DP0, and DPS = 1 selects the second bank, DP1 Watchdog Timer Reset and EEPROM Ready/Busy Flag. Each time this bit is set to "1" by user software, a pulse is generated to reset the watchdog timer. The WDTRST bit is then automatically reset to "0" in the next instruction cycle. The WDTRST bit is Write-Only. This bit also serves as the RDY/BSY flag in a Read-Only mode during EEPROM write. RDY/BSY = 1 means that the EEPROM is ready to be programmed. While programming operations are being executed, the RDY/BSY bit equals "0" and is automatically reset to "1" when programming is completed. Watchdog Timer Enable Bit. WDTEN = 1 enables the watchdog timer and WDTEN = 0 disables the watchdog timer.

WDTEN

4-111

Table 4. SPCR--SPI Control Register
SPCR Address = D5H Reset Value = 0000 01XXB

SPIE Bit Symbol SPIE SPE DORD MSTR CPOL CPHA SPR0 SPR1 7 Function

SPE 6

DORD 5

MSTR 4

CPOL 3

CPHA 2

SPR1 1

SPR0 0

SPI Interrupt Enable. This bit, in conjunction with the ES bit in the IE register, enables SPI interrupts: SPIE = 1 and ES = 1 enable SPI interrupts. SPIE = 0 disables SPI interrupts. SPI Enable. SPI = 1 enables the SPI channel and connects SS, MOSI, MISO and SCK to pins P1.4, P1.5, P1.6, and P1.7. SPI = 0 disables the SPI channel. Data Order. DORD = 1 selects LSB first data transmission. DORD = 0 selects MSB first data transmission. Master/Slave Select. MSTR = 1 selects Master SPI mode. MSTR = 0 selects Slave SPI mode. Clock Polarity. When CPOL = 1, SCK is high when idle. When CPOL = 0, SCK of the master device is low when not transmitting. Please refer to figure on SPI Clock Phase and Polarity Control. Clock Phase. The CPHA bit together with the CPOL bit controls the clock and data relationship between master and slave. Please refer to figure on SPI Clock Phase and Polarity Control. SPI Clock Rate Select. These two bits control the SCK rate of the device configured as master. SPR1 and SPR0 have no effect on the slave. The relationship between SCK and the oscillator frequency, FOSC., is as follows: SPR1 SPR0 SCK = FOSC. divided by 0 0 4 0 1 16 1 0 64 1 1 128

Table 5. SPSR--SPI Status Register
SPSR Address = AAH Reset Value = 00XX XXXXB

SPIF Bit Symbol SPIF 7 Function

WCOL 6

-- 5

-- 4

-- 3

-- 2

-- 1

-- 0

SPI Interrupt Flag. When a serial transfer is complete, the SPIF bit is set and an interrupt is generated if SPIE = 1 and ES = 1. The SPIF bit is cleared by reading the SPI status register with SPIF and WCOL bits set, and then accessing the SPI data register. Write Collision Flag. The WCOL bit is set if the SPI data register is written during a data transfer. During data transfer, the result of reading the SPDR register may be incorrect, and writing to it has no effect. The WCOL bit (and the SPIF bit) are cleared by reading the SPI status register with SPIF and WCOL set, and then accessing the SPI data register.

WCOL

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Table 6. SPDR--SPI Data Register
SPDR Address = 86H Reset Value = unchanged

SPD7 Bit 7

SPD6 6

SPD5 5

SPD4 4

SPD3 3

SPD2 2

SPD1 1

SPD0 0

Data Memory--EEPROM and RAM
The AT89S8252 implements 2K bytes of on-chip EEPROM for data storage and 256 bytes of RAM. The upper 128 bytes of RAM occupy a parallel space to the Special Function Registers. That means the upper 128 bytes have the same addresses as the SFR space but are physically separate from SFR space. When an instruction accesses an internal location above address 7FH, the address mode used in the instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space. Instructions that use direct addressing access SFR space. For example, the following direct addressing instruction accesses the SFR at location 0A0H (which is P2).
MOV 0A0H, #data

Programmable Watchdog Timer
The programmable Watchdog Timer (WDT) operates from an independent oscillator. The prescaler bits, PS0, PS1 and PS2 in SFR WMCON are used to set the period of the Watchdog Timer from 16 ms to 2048 ms. The available timer periods are shown in the following table and the actual timer periods (at VCC = 5V) are within 30% of the nominal. The WDT is disabled by Power-on Reset and during Power Down. It is enabled by setting the WDTEN bit in SFR WMCON (address = 96H). The WDT is reset by setting the WDTRST bit in WMCON. When the WDT times out without being reset or disabled, an internal RST pulse is generated to reset the CPU. Table 7. Watchdog Timer Period Selection
WDT Prescaler Bits PS2 0 0 0 0 1 1 1 1 PS1 0 0 1 1 0 0 1 1 PS0 0 1 0 1 0 1 0 1 16 ms 32 ms 64 ms 128 ms 256 ms 512 ms 1024 ms 2048 ms Period (nominal)

Instructions that use indirect addressing access the upper 128 bytes of RAM. For example, the following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte at address 0A0H, rather than P2 (whose address is 0A0H).
MOV @R0, #data

Note that stack operations are examples of indirect addressing, so the upper 128 bytes of data RAM are available as stack space. The on-chip EEPROM data memory is selected by setting the EEMEN bit in the WMCON register at SFR address location 96H. The EEPROM address range is from 000H to 7FFH. The MOVX instructions are used to access the EEPROM. To access off-chip data memory with the MOVX instructions, the EEMEN bit needs to be set to "0". The EEMWE bit in the WMCON register needs to be set to "1" before any byte location in the EEPROM can be written. User software should reset EEMWE bit to "0" if no further EEPROM write is required. EEPROM write cycles in the serial programming mode are self-timed and typically take 2.5 ms. The progress of EEPROM write can be monitored by reading the RDY/BSY bit (read-only) in SFR WMCON. RDY/BSY = 0 means programming is still in progress and RDY/BSY = 1 means EEPROM write cycle is completed and another write cycle can be initiated. In addition, during EEPROM programming, an attempted read from the EEPROM will fetch the byte being written with the MSB complemented. Once the write cycle is completed, true data are valid at all bit locations.

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Timer 0 and 1
Timer 0 and Timer 1 in the AT89S8252 operate the same way as Timer 0 and Timer 1 in the AT89C51, AT89C52 and AT89C55. For further information, see the October 1995 Microcontroller Data Book, page 2-45, section titled, "Timer/Counters."

Table 8. Timer 2 Operating Modes
RCLK + TCLK 0 0 1 X CP/RL2 0 1 X X TR2 1 1 1 0 MODE 16-bit Auto-Reload 16-bit Capture Baud Rate Generator (Off)

Timer 2
Timer 2 is a 16 bit Timer/Counter that can operate as either a timer or an event counter. The type of operation is selected by bit C/T2 in the SFR T2CON (shown in Table 2). Timer 2 has three operating modes: capture, auto-reload (up or down counting), and baud rate generator. The modes are selected by bits in T2CON, as shown in Table 8. Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2 register is incremented every machine cycle. Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the oscillator frequency. In the Counter function, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, T2. In this function, the external input is sampled during S5P2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. To ensure that a given level is sampled at least once before it changes, the level should be held for at least one full machine cycle. Figure 1. Timer 2 in Capture Mode
OSC 12 C/T2 = 0

Capture Mode
In the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 is a 16 bit timer or counter which upon overflow sets bit TF2 in T2CON. This bit can then be used to generate an interrupt. If EXEN2 = 1, Timer 2 performs the same operation, but a lto-0 transition at external input T2EX also causes the current value in TH2 and TL2 to be captured into RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit EXF2 in T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt. The capture mode is illustrated in Figure 1.

Auto-Reload (Up or Down Counter)
Timer 2 can be programmed to count up or down when configured in its 16 bit auto-reload mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the SFR T2MOD (see Table 9). Upon reset, the DCEN bit is set to 0 so that timer 2 will default to count up. When DCEN is set, Timer 2 can count up or down, depending on the value of the T2EX pin. Figure 2 shows Timer 2 automatically counting up when DCEN = 0. In this mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 counts up to

TH2 CONTROL C/T2 = 1 T2 PIN TRANSITION DETECTOR T2EX PIN CONTROL EXEN2 EXF2 TR2 CAPTURE

TL2

TF2 OVERFLOW

RCAP2H RCAP2L TIMER 2 INTERRUPT

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0FFFFH and then sets the TF2 bit upon overflow. The overflow also causes the timer registers to be reloaded with the 16 bit value in RCAP2H and RCAP2L. The values in RCAP2H and RCAP2L are preset by software. If EXEN2 = 1, a 16 bit reload can be triggered either by an overflow or by a 1-to-0 transition at external input T2EX. This transition also sets the EXF2 bit. Both the TF2 and EXF2 bits can generate an interrupt if enabled. Setting the DCEN bit enables Timer 2 to count up or down, as shown in Figure 3. In this mode, the T2EX pin controls the direction of the count. A logic 1 at T2EX makes Timer 2 count up. The timer will overflow at 0FFFFH and set the TF2 bit. This overflow also causes the 16 bit value in Figure 2. Timer 2 in Auto Reload Mode (DCEN = 0) RCAP2H and RCAP2L to be reloaded into the timer registers, TH2 and TL2, respectively. A logic 0 at T2EX makes Timer 2 count down. The timer underflows when TH2 and TL2 equal the values stored in RCAP2H and RCAP2L. The underflow sets the TF2 bit and causes 0FFFFH to be reloaded into the timer registers. The EXF2 bit toggles whenever Timer 2 overflows or underflows and can be used as a 17th bit of resolution. In this operating mode, EXF2 does not flag an interrupt.

Table 9. T2MOD--Timer 2 Mode Control Register
T2MOD Address = 0C9H Not Bit Addressable -- Bit Symbol -- T2OE DCEN 7 Function Not implemented, reserved for future use. Timer 2 Output Enable bit. When set, this bit allows Timer 2 to be configured as an up/down counter. -- 6 -- 5 -- 4 -- 3 -- 2 T2OE 1 DCEN 0 Reset Value = XXXX XX00B

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Figure 3. Timer 2 Auto Reload Mode (DCEN = 1)

Figure 4. Timer 2 in Baud Rate Generator Mode
TIMER 1 OVERFLOW

2
"0" NOTE: OSC. FREQ. IS DIVIDED BY 2, NOT 12 SMOD1 OSC "1"

2

C/T2 = 0 "1" TH2 CONTROL TR2 C/T2 = 1 "1" "0" TCLK Tx CLOCK TL2 RCLK Rx CLOCK "0"

16

T2 PIN RCAP2H RCAP2L TRANSITION DETECTOR T2EX PIN CONTROL EXEN2 EXF2 TIMER 2 INTERRUPT

16

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AT89S8252
Baud Rate Generator
Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON (Table 2). Note that the baud rates for transmit and receive can be different if Timer 2 is used for the receiver or transmitter and Timer 1 is used for the other function. Setting RCLK and/or TCLK puts Timer 2 into its baud rate generator mode, as shown in Figure 4. The baud rate generator mode is similar to the auto-reload mode, in that a rollover in TH2 causes the Timer 2 registers to be reloaded with the 16 bit value in registers RCAP2H and RCAP2L, which are preset by software. The baud rates in Modes 1 and 3 are determined by Timer 2's overflow rate according to the following equation. Timer 2 Overflow Rate Modes 1 and 3 Baud Rates = ----------------------------------------------------------16 The Timer can be configured for either timer or counter operation. In most applications, it is configured for timer operation (CP/T2 = 0). The timer operation is different for Timer 2 when it is used as a baud rate generator. Normally, as a timer, it increments every machine cycle (at 1/12 the oscillator frequency). As a baud rate generator, however, it increments every state time (at 1/2 the oscillator frequency). The baud rate formula is given below. Figure 5. Timer 2 in Clock-Out Mode Modes 1 and 3 Oscillator Frequency -------------------------------------- = --------------------------------------------------------------------------------------------Baud Rate 32 [ 65536 ( RCAP2H,RCAP2L ) ] where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16 bit unsigned integer. Timer 2 as a baud rate generator is shown in Figure 4. This figure is valid only if RCLK or TCLK = 1 in T2CON. Note that a rollover in TH2 does not set TF2 and will not generate an interrupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus when Timer 2 is in use as a baud rate generator, T2EX can be used as an extra external interrupt. Note that when Timer 2 is running (TR2 = 1) as a timer in the baud rate generator mode, TH2 or TL2 should not be read from or written to. Under these conditions, the Timer is incremented every state time, and the results of a read or write may not be accurate. The RCAP2 registers may be read but should not be written to, because a write might overlap a reload and cause write and/or reload errors. The timer should be turned off (clear TR2) before accessing the Timer 2 or RCAP2 registers.

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Programmable Clock Out
A 50% duty cycle clock can be programmed to come out on P1.0, as shown in Figure 5. This pin, besides being a regular I/0 pin, has two alternate functions. It can be programmed to input the external clock for Timer/Counter 2 or to output a 50% duty cycle clock ranging from 61 Hz to 4 MHz at a 16 MHz operating frequency. To configure the Timer/Counter 2 as a clock generator, bit C/T2 (T2CON.1) must be cleared and bit T2OE (T2MOD.1) must be set. Bit TR2 (T2CON.2) starts and stops the timer. The clock-out frequency depends on the oscillator frequency and the reload value of Timer 2 capture registers (RCAP2H, RCAP2L), as shown in the following equation.
Oscillator Frequency Clock Out Frequency = -----------------------------------------------------------------------------------------4 [ 65536 ( RCAP2H,RCAP2L ) ]

UART
The UART in the AT89S8252 operates the same way as the UART in the AT89C51, AT89C52 and AT89C55. For further information, see the October 1995 Microcontroller Data Book, page 2-49, section titled, "Serial Interface."

Serial Peripheral Interface
The serial peripheral interface (SPI) allows high-speed synchronous data transfer between the AT89S8252 and peripheral devices or between several AT89S8252 devices. The AT89S8252 SPI features include the following: Full-Duplex, 3-Wire Synchronous Data Transfer Master or Slave Operation 1.5-MHz Bit Frequency (max.) LSB First or MSB First Data Transfer Four Programmable Bit Rates End of Transmission Interrupt Flag Write Collision Flag Protection Wakeup from Idle Mode (Slave Mode Only)

In the clock-out mode, Timer 2 rollovers will not generate an interrupt. This behavior is similar to when Timer 2 is used as a baud-rate generator. It is possible to use Timer 2 as a baud-rate generator and a clock generator simultaneously. Note, however, that the baud-rate and clock-out frequencies cannot be determined independently from one another since they both use RCAP2H and RCAP2L. Figure 6. SPI Block Diagram

S OSCILLATOR MSB LSB
8/16-BIT SHIFT REGISTER

S

DIVIDER 41664128

READ DATA BUFFER

SPI CLOCK (MASTER)

CLOCK CLOCK LOGIC S M

PIN CONTROL LOGIC

M M

MISO P1.6 MOSI P1.5

SELECT
SPR1 SPR0

SCK 1.7 SS P1.4

SPI CONTROL
WCOL SPIF

MSTR SPE
DORD MSTR CPHA CPOL SPR1 SPR0

SPIE

8

SPI STATUS REGISTER

SPI CONTROL REGISTER

8

8

SPI INTERRUPT INTERNAL REQUEST DATA BUS

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AT89S8252

SPE

DORD

MSTR

SPE

AT89S8252
The interconnection between master and slave CPUs with SPI is shown in the following figure. The SCK pin is the clock output in the master mode but is the clock input in the slave mode. Writing to the SPI data register of the master CPU starts the SPI clock generator, and the data written shifts out of the MOSI pin and into the MOSI pin of the slave CPU. After shifting one byte, the SPI clock generator stops, setting the end of transmission flag (SPIF). If both the SPI interrupt enable bit (SPIE) and the serial port interrupt enable bit (ES) are set, an interrupt is requested. The Slave Select input, SS/P1.4, is set low to select an individual SPI device as a slave. When SS/P1.4 is set high, the SPI port is deactivated and the MOSI/P1.5 pin can be used as an input. There are four combinations of SCK phase and polarity with respect to serial data, which are determined by control bits CPHA and CPOL. The SPI data transfer formats are shown in Figures 8 and 9.

Figure 7. SPI Master-Slave Interconnection
MSB MASTER LSB
MISO MISO

MSB

SLAVE

LSB

8-BIT SHIFT REGISTER
MOSI MOSI

8-BIT SHIFT REGISTER

SPI CLOCK GENERATOR

SCK SS VCC

SCK SS

Figure 8. SPI transfer Format with CPHA = 0

*Not defined but normally MSB of character just received

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Figure 9. SPI Transfer Format with CPHA = 1
SCK CYCLE # (FOR REFERENCE) SCK (CPOL=0) SCK (CPOL=1) MOSI (FROM MASTER) MISO (FROM SLAVE) SS (TO SLAVE)
MSB 6 6 5 5 4 4 3 3 2 2 1 1 LSB LSB

1

2

3

4

5

6

7

8

*

MSB

*Not defined but normally LSB of previously transmitted character

Interrupts
The AT89S8252 has a total of six interrupt vectors: two external interrupts (INT0 and INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. These interrupts are all shown in Figure 10. Each of these interrupt sources can be individually enabled or disabled by setting or clearing a bit in Special Function Register IE. IE also contains a global disable bit, EA, which disables all interrupts at once. Note that Table 10 shows that bit position IE.6 is unimplemented. In the AT89C51, bit position IE.5 is also unimplemented. User software should not write 1s to these bit positions, since they may be used in future AT89 products. Table 10. Interrupt Enable (IE) Register
(MSB) EA -- ET2 ES ET1 EX1 ET0 (LSB) EX0

Timer 2 interrupt is generated by the logical OR of bits TF2 and EXF2 in register T2CON. Neither of these flags is cleared by hardware when the service routine is vectored to. In fact, the service routine may have to determine whether it was TF2 or EXF2 that generated the interrupt, and that bit will have to be cleared in software. The Timer 0 and Timer 1 flags, TF0 and TF1, are set at S5P2 of the cycle in which the timers overflow. The values are then polled by the circuitry in the next cycle. However, the Timer 2 flag, TF2, is set at S2P2 and is polled in the same cycle in which the timer overflows.

Figure 10. Interrupt Sources

Enable Bit = 1 enables the interrupt. Enable Bit = 0 disables the interrupt. Symbol Position Function Disables all interrupts. If EA = 0, no interrupt is acknowledged. If EA = 1, each interrupt source is individually enabled or disabled by setting or clearing its enable bit. Reserved. Timer 2 interrupt enable bit. SPI and UART interrupt enable bit. Timer 1 interrupt enable bit. External interrupt 1 enable bit. Timer 0 interrupt enable bit. External interrupt 0 enable bit.

EA

IE.7

-- ET2 ES ET1 EX1 ET0 EX0

IE.6 IE.5 IE.4 IE.3 IE.2 IE.1 IE.0

User software should never write 1s to unimplemented bits, because they may be used in future AT89 products.

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AT89S8252
Figure 11. Oscillator Connections Figure 12. External Clock Drive Configuration

Note:

Note: C1, C2 = 30 pF 10 pF for Crystals = 40 pF 10 pF for Ceramic Resonators

Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator, as shown in Figure 11. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven, as shown in Figure 12. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.

internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when idle mode is terminated by a reset, the instruction following the one that invokes idle mode should not write to a port pin or to external memory.

Power Down Mode
In the power down mode, the oscillator is stopped and the instruction that invokes power down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode is terminated. Exit from power down can be initiated either by a hardware reset or by an enabled external interrupt. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize. To exit power down via an interrupt, the external interrupt must be enabled as level sensitive before entering power down. The interrupt service routine starts at 16 ms (nominal) after the enabled interrupt pin is activated.

Idle Mode
In idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. Note that when idle mode is terminated by a hardware reset, the device normally resumes program execution from where it left off, up to two machine cycles before the

Status of External Pins During Idle and Power Down Modes
Mode Idle Idle Power Down Power Down Program Memory Internal External Internal External ALE 1 1 0 0 PSEN 1 1 0 0 PORT0 Data Float Data Float PORT1 Data Data Data Data PORT2 Data Address Data Data PORT3 Data Data Data Data

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Program Memory Lock Bits
The AT89S8252 has three lock bits that can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the following table. When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value and holds that value until reset is activated. The latched value of EA must agree with the current logic level at that pin in order for the device to function properly. Once programmed, the lock bits can only be unprogrammed with the Chip Erase operations in either the parallel or serial modes.

Lock Bit Protection Modes(1)(2)
Program Lock Bits LB1 1 2 U P LB2 U U LB3 U U No internal memory lock feature. MOVC instructions executed from external program memory are disabled from fetching code bytes from internal memory. EA is sampled and latched on reset and further programming of the Flash memory (parallel or serial mode) is disabled. Same as Mode 2, but parallel or serial verify are also disabled. Same as Mode 3, but external execution is also disabled. Protection Type

3 4 Notes:

P P

P P

U P

1. U = Unprogrammed 2. P = Programmed

Programming the Flash and EEPROM
Atmel's AT89S8252 Flash Microcontroller offers 8K bytes of in-system reprogrammable Flash Code memory and 2K bytes of EEPROM Data memory. The AT89S8252 is normally shipped with the on-chip Flash Code and EEPROM Data memory arrays in the erased state (i.e. contents = FFH) and ready to be programmed. This device supports a High-Voltage (12V) Parallel programming mode and a Low-Voltage (5V) Serial programming mode. The serial programming mode provides a convenient way to download the AT89S8252 inside the user's system. The parallel programming mode is compatible with conventional third party Flash or EPROM programmers. The Code and Data memory arrays are mapped via separate address spaces in the serial programming mode. In the parallel programming mode, the two arrays occupy one contiguous address space: 0000H to 1FFFH for the Code array and 2000H to 27FFH for the Data array. The Code and Data memory arrays on the AT89S8252 are programmed byte-by-byte in either programming mode. An auto-erase cycle is provided with the self-timed programming operation in the serial programming mode. There is no need to perform the Chip Erase operation to reprogram any memory location in the serial programming mode unless any of the lock bits have been programmed. In the parallel programming mode, there is no auto-erase cycle. To reprogram any non-blank byte, the user needs to use the Chip Erase operation first to erase both arrays.

Parallel Programming Algorithm
To program and verify the AT89S8252 in the parallel programming mode, the following sequence is recommended: 1. Power-up sequence: Apply power between VCC and GND pins. Set RST pin to "H". Apply a 3 MHz to 24 MHz clock to XTAL1 pin and wait for at least 10 milliseconds. 2. Set PSEN pin to "L" ALE pin to "H" EA pin to "H" and all other pins to "H". 3. Apply the appropriate combination of "H" or "L" logic levels to pins P2.6, P2.7, P3.6, P3.7 to select one of the programming operations shown in the Flash Programming Modes table. 4. Apply the desired byte address to pins P1.0 to P1.7 and P2.0 to P2.5. Apply data to pins P0.0 to P0.7 for Write Code operation. 5. Raise EA/VPP to 12V to enable Flash programming, erase or verification. 6. Pulse ALE/PROG once to program a byte in the Code memory array, the Data memory array or the lock bits. The byte-write cycle is self-timed and typically takes 1.5 ms. 7. To verify the byte just programmed, bring pin P2.7 to "L" and read the programmed data at pins P0.0 to P0.7.

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8. Repeat steps 3 through 7 changing the address and data for the entire 2K or 8K bytes array or until the end of the object file is reached. 9. Power-off sequence: Set XTAL1 to "L". Set RST and EA pins to "L". Turn VCC power off. In the parallel programming mode, there is no auto-erase cycle and to reprogram any non-blank byte, the user needs to use the Chip Erase operation first to erase both arrays.

Serial Programming Fuse
A programmable fuse is available to disable Serial Programming if the user needs maximum system security. The Serial Programming Fuse can only be programmed or erased in the Parallel Programming Mode. The AT89S8252 is shipped with the Serial Programming Mode enabled. Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of locations 030H and 031H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned are as follows: (030H) = 1EH indicates manufactured by Atmel (031H) = 72H indicates 89S8252

DATA Polling
The AT89S8252 features DATA Polling to indicate the end of a write cycle. During a write cycle in the parallel or serial programming mode, an attempted read of the last byte written will result in the complement of the written datum on P0.7 (parallel mode), and on the MSB of the serial output byte on MISO (serial mode). Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. DATA Polling may begin any time after a write cycle has been initiated.

Programming Interface
Every code byte in the Flash and EEPROM arrays can be written, and the entire array can be erased, by using the appropriate combination of control signals. The write operation cycle is self-timed and once initiated, will automatically time itself to completion. All major programming vendors offer worldwide support for the Atmel microcontroller series. Please contact your local programming vendor for the appropriate software revision.

Ready/Busy
The progress of byte programming in the parallel programming mode can also be monitored by the RDY/BSY output signal. Pin P3.4 is pulled Low after ALE goes High during programming to indicate BUSY. P3.4 is pulled High again when programming is done to indicate READY.

Serial Downloading
Both the Code and Data memory arrays can be programmed using the serial SPI bus while RST is pulled to VCC. The serial interface consists of pins SCK, MOSI (input) and MISO (output). After RST is set high, the Programming Enable instruction needs to be executed first before program/erase operations can be executed. An auto-erase cycle is built into the self-timed programming operation (in the serial mode ONLY) and there is no need to first execute the Chip Erase instruction unless any of the lock bits have been programmed. The Chip Erase operation turns the content of every memory location in both the Code and Data arrays into FFH. The Code and Data memory arrays have separate address spaces: 0000H to 1FFFH for Code memory and 000H to 7FFH for Data memory. Either an external system clock is supplied at pin XTAL1 or a crystal needs to be connected across pins XTAL1 and XTAL2. The maximum serial clock (SCK) frequency should be less than 1/40 of the crystal frequency. With a 24 MHz oscillator clock, the maximum SCK frequency is 600 kHz.

Program Verify
If lock bits LB1 and LB2 have not been programmed, the programmed Code or Data byte can be read back via the address and data lines for verification. The state of the lock bits can also be verified directly in the parallel programming mode. In the serial programming mode, the state of the lock bits can only be verified indirectly by observing that the lock bit features are enabled.

Chip Erase
Both Flash and EEPROM arrays are erased electrically at the same time. In the parallel programming mode, chip erase is initiated by using the proper combination of control signals and by holding ALE/PROG low for 10 ms. The Code and Data arrays are written with all "1"s in the Chip Erase operation. In the serial programming mode, a chip erase operation is initiated by issuing the Chip Erase instruction. In this mode, chip erase is self-timed and takes about 16 ms. During chip erase, a serial read from any address location will return 00H at the data outputs.

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Serial Programming Algorithm
To program and verify the AT89S8252 in the serial programming mode, the following sequence is recommended: 1. Power-up sequence: Apply power between VCC and GND pins. Set RST pin to "H". If a crystal is not connected across pins XTAL1 and XTAL2, apply a 3 MHz to 24 MHz clock to XTAL1 pin and wait for at least 10 milliseconds. 2. Enable serial programming by sending the Programming Enable serial instruction to pin MOSI/P1.5. The frequency of the shift clock supplied at pin SCK/P1.7 needs to be less than the CPU clock at XTAL1 divided by 40. 3. The Code or Data array is programmed one byte at a time by supplying the address and data together with the appropriate Write instruction. The selected memory location is first automatically erased before new data is

written. The write cycle is self-timed and typically takes less than 2.5 ms at 5V. 4. Any memory location can be verified by using the Read instruction which returns the content at the selected address at serial output MISO/P1.6. 5. At the end of a programming session, RST can be set low to commence normal operation. Power-off sequence (if needed): Set XTAL1 to "L" (if a crystal is not used). Set RST to "L". Turn VCC power off.

Serial Programming Instruction
The Instruction Set for Serial Programming follows a 3-byte protocol and is shown in the following table:

Instruction Set
Instruction Byte 1 Programming Enable Chip Erase Read Code Memory 1010 1100 1010 1100 aaaa a001 Input Format Byte 2 0101 0011 xxxx x100 low addr Byte 3 xxxx xxxx xxxx xxxx xxxx xxxx Enable serial programming interface after RST goes high. Chip erase both 8K & 2K memory arrays. Read data from Code memory array at the selected address. The 5 MSBs of the first byte are the high order address bits. The low order address bits are in the second byte. Data are available at pin MISO during the third byte. Write data to Code memory location at selected address. The address bits are the 5 MSBs of the first byte together with the second byte. Read data from Data memory array at selected address. Data are available at pin MISO during the third byte. Write data to Data memory location at selected address. Write lock bits. Set LB1, LB2 or LB3 = "0" to program lock bits. Operation

Write Code Memory

aaaa a010

low addr

data in

Read Data Memory Write Data Memory Write Lock Bits

00aa a101 00aa a110 1010 1100

low addr low addr
LB1 LB2 LB3

xxxx xxxx data in xxxx xxxx

x x111

Notes:

1. DATA polling is used to indicate the end of a write cycle which typically takes less than 2.5 ms at 5V. 2. "aaaaa" = high order address. 3. "x" = don't care.

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Flash and EEPROM Parallel Programming Modes
Mode Serial Prog. Modes Chip Erase Write (10K bytes) Memory Read (10K bytes) Memory Write Lock Bits: Bit - 1 Bit - 2 Bit - 3 Read Lock Bits: Bit - 1 Bit - 2 Bit - 3 Read Atmel Code Read Device Code Serial Prog. Enable Serial Prog. Disable Read Serial Prog. Fuse H H H H H L L L L L H H H (2) (2) 12V 12V 12V 12V 12V L L L L H L L H H H L L L L L L L H H H H L H 12V H H L L RST H H H H H PSEN h(1) L L L L H ALE/PROG h(1) (2) EA/VPP x 12V 12V 12V 12V H L L H L H L L L H H H L H H L X DIN DOUT DIN P0.7 = 0 P0.6 = 0 P0.5 = 0 DOUT @P0.2 @P0.1 @P0.0 DOUT DOUT P0.0 = 0 P0.0 = 1 @P0.0 X ADDR ADDR X X X X X X X X 30H 31H X X X P2.6 P2.7 P3.6 P3.7 Data I/O P0.7:0 Address P2.5:0 P1.7:0

Notes:

1. "h" = weakly pulled "High" internally. 2. Chip Erase and Serial Programming Fuse require a 10-ms PROG pulse. Chip Erase needs to be performed first before reprogramming any byte with a content other than FFH. 3. P3.4 is pulled Low during programming to indicate RDY/BSY. 4. "X" = don't care

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Figure 14. Programming the Flash/EEPROM Memory
+5V

Figure 15. Flash/EEPROM Serial Downloading
+4.0V to 6.0V

AT89S8252
A0 - A7 ADDR. 0000H/27FFH A8 - A13 P2.6 SEE FLASH PROGRAMMING MODES TABLE P2.7 P3.6 P3.7 XTAL2 EA VPP ALE P1 P2.0 - P2.5 VCC P0 PGM DATA INSTRUCTION INPUT DATA OUTPUT CLOCK IN

AT89S8252
VCC

P1.5/MOSI P1.6/MISO P1.7/SCK

PROG

XTAL2

3-24 MHz

3-24 MHz

XTAL1 GND

RST PSEN

VIH

XTAL1 GND

RST

VIH

Figure 16. Verifying the Flash/EEPROM Memory
+5V

AT89S8252
ADDR. 0000H/27FFH A0 - A7 P1 P2.0 - P2.5 P2.6 P2.7 P3.6 P3.7 XTAL2 EA VPP VCC P0 PGM DATA (USE 10K PULLUPS) VIH

A8 - A13

SEE FLASH PROGRAMMING MODES TABLE

ALE

3-24 MHz

XTAL1 GND

RST PSEN

VIH

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Flash Programming and Verification Characteristics-Parallel Mode
TA = 0C to 70C, VCC = 5.0V 10%
Symbol VPP IPP 1/tCLCL tAVGL tGHAX tDVGL tGHDX tEHSH tSHGL tGLGH tAVQV tELQV tEHQZ tGHBL tWC Parameter Programming Enable Voltage Programming Enable Current Oscillator Frequency Address Setup to PROG Low Address Hold After PROG Data Setup to PROG Low Data Hold After PROG P2.7 (ENABLE) High to VPP VPP Setup to PROG Low PROG Width Address to Data Valid ENABLE Low to Data Valid Data Float After ENABLE PROG High to BUSY Low Byte Write Cycle Time 0 3 48tCLCL 48tCLCL 48tCLCL 48tCLCL 48tCLCL 10 1 110 48tCLCL 48tCLCL 48tCLCL 1.0 2.0 s ms s s Min 11.5 Max 12.5 1.0 24 Units V mA MHz

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Flash/EEPROM Programming and Verification Waveforms - Parallel Mode

Serial Downloading Waveforms
SERIAL CLOCK INPUT SCK/P1.7
7 6 5 4 3 2 1 0

SERIAL DATA INPUT MOSI/P1.5 SERIAL DATA OUTPUT MISO/P1.6
MSB LSB MSB LSB

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Absolute Maximum Ratings*
Operating Temperature .................................. -55C to +125C Storage Temperature ..................................... -65C to +150C Voltage on Any Pin with Respect to Ground .....................................-1.0V to +7.0V Maximum Operating Voltage............................................. 6.6V DC Output Current...................................................... 15.0 mA *NOTICE: Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

DC Characteristics
The values shown in this table are valid for TA = -40C to 85C and VCC = 5.0V 20%, unless otherwise noted.
Symbol VIL VIL1 VIH VIH1 VOL VOL1 Parameter Input Low Voltage Input Low Voltage (EA) Input High Voltage Input High Voltage Output Low Voltage (1) (Ports 1,2,3) Output Low Voltage (1) (Port 0, ALE, PSEN) Output High Voltage (Ports 1,2,3, ALE, PSEN) (Except XTAL1, RST) (XTAL1, RST) IOL = 1.6 mA IOL = 3.2 mA IOH = -60 A, VCC = 5V 10% VOH IOH = -25 A IOH = -10 A IOH = -800 A, VCC = 5V 10% VOH1 Output High Voltage (Port 0 in External Bus Mode) Logical 0 Input Current (Ports 1,2,3) Logical 1 to 0 Transition Current (Ports 1,2,3) Input Leakage Current (Port 0, EA) Reset Pulldown Resistor Pin Capacitance Power Supply Current Idle Mode, 12 MHz ICC Power Down Mode (2) Notes: VCC = 6V VCC = 3V 1. Under steady state (non-transient) conditions, IOL must be externally limited as follows: Maximum IOL per port pin: 10 mA Maximum IOL per 8-bit port: Port 0: 26 mA Ports 1, 2, 3: 15 mA 6.5 100 40 mA A A Test Freq. = 1 MHz, TA = 25C Active Mode, 12 MHz IOH = -300 A IOH = -80 A IIL ITL ILI RRST CIO VIN = 0.45V VIN = 2V, VCC = 5V 10% 0.45 < VIN < VCC 50 2.4 0.75 VCC 0.9 VCC 2.4 0.75 VCC 0.9 VCC -50 -650 10 300 10 25 Condition (Except EA) Min -0.5 -0.5 0.2 VCC + 0.9 0.7 VCC Max 0.2 VCC - 0.1 0.2 VCC - 0.3 VCC + 0.5 VCC + 0.5 0.5 0.5 Units V V V V V V V V V V V V A A A K pF mA

Maximum total IOL for all output pins: 71 mA If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test conditions. 2. Minimum VCC for Power Down is 2V

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AC Characteristics
Under operating conditions, load capacitance for Port 0, ALE/PROG, and PSEN = 100 pF; load capacitance for all other outputs = 80 pF.

External Program and Data Memory Characteristics
Variable Oscillator Symbol 1/tCLCL tLHLL tAVLL tLLAX tLLIV tLLPL tPLPH tPLIV tPXIX tPXIZ tPXAV tAVIV tPLAZ tRLRH tWLWH tRLDV tRHDX tRHDZ tLLDV tAVDV tLLWL tAVWL tQVWX tQVWH tWHQX tRLAZ tWHLH Parameter Oscillator Frequency ALE Pulse Width Address Valid to ALE Low Address Hold After ALE Low ALE Low to Valid Instruction In ALE Low to PSEN Low PSEN Pulse Width PSEN Low to Valid Instruction In Input Instruction Hold After PSEN Input Instruction Float After PSEN PSEN to Address Valid Address to Valid Instruction In PSEN Low to Address Float RD Pulse Width WR Pulse Width RD Low to Valid Data In Data Hold After RD Data Float After RD ALE Low to Valid Data In Address to Valid Data In ALE Low to RD or WR Low Address to RD or WR Low Data Valid to WR Transition Data Valid to WR High Data Hold After WR RD Low to Address Float RD or WR High to ALE High tCLCL - 20 3tCLCL - 50 4tCLCL - 75 tCLCL - 20 7tCLCL - 120 tCLCL - 20 0 tCLCL + 25 0 2tCLCL - 28 8tCLCL - 150 9tCLCL - 165 3tCLCL + 50 6tCLCL - 100 6tCLCL - 100 5tCLCL - 90 tCLCL - 8 5tCLCL - 55 10 0 tCLCL - 10 tCLCL - 13 3tCLCL - 20 3tCLCL - 45 Min 0 2tCLCL - 40 tCLCL - 13 tCLCL - 20 4tCLCL - 65 Max 24 Units MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns

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External Program Memory Read Cycle

External Data Memory Read Cycle

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External Data Memory Write Cycle

External Clock Drive Waveforms

External Clock Drive
Symbol Parameter Min 1/tCLCL tCLCL tCHCX tCLCX tCLCH tCHCL Oscillator Frequency Clock Period High Time Low Time Rise Time Fall Time 0 41.6 15 15 20 20 VCC = 4.0V to 6.0V Max 24 MHz ns ns ns ns ns Units

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Serial Port Timing: Shift Register Mode Test Conditions
The values in this table are valid for VCC = 4.0V to 6V and Load Capacitance = 80 pF.
Symbol Parameter Variable Oscillator Min tXLXL tQVXH tXHQX tXHDX tXHDV Serial Port Clock Cycle Time Output Data Setup to Clock Rising Edge Output Data Hold After Clock Rising Edge Input Data Hold After Clock Rising Edge Clock Rising Edge to Input Data Valid 12tCLCL 10tCLCL - 133 2tCLCL - 117 0 10tCLCL - 133 Max s ns ns ns ns Units

Shift Register Mode Timing Waveforms

AC Testing Input/Output Waveforms(1)

Float Waveforms(1)

Notes:

1.

AC Inputs during testing are driven at V CC - 0.5V for a logic 1 and 0.45V for a logic 0. Timing measurements are made at VIH min. for a logic 1 and VIL max. for a logic 0.

Notes:

1.

For timing purposes, a port pin is no longer floating when a 100 mV change from load voltage occurs. A port pin begins to float when a 100 mV change from the loaded VOH/VOL level occurs.

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AT89S8252
24 TYPICAL ICC (ACTIVE) at 25C
VCC = 6.0V

I C 16 C 12 m A 8
4 0 0 4 8 12 16

20

VCC = 5.0V

20

24

F (MHz)

AT89S8252
4.8 4.0

TYPICAL ICC (IDLE) at 25C
VCC = 6.0V

I C 3.2 C 2.4 m 1.6 A
0.8

VCC = 5.0V

0.0
0 4 8 12 16 20 24

F (MHz)

Notes:

1. 2.

XTAL1 tied to GND for Icc (power down) Lock bits programmed

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AT89S8252

AT89S8252
Ordering Information
Speed (MHz) 16 Power Supply 4.0V to 6.0V Ordering Code AT89S8252-16AA AT89S8252-16JA AT89S8252-16PA AT89S8252-16QA AT89S8252-24AC AT89S8252-24JC AT89S8252-24PC AT89S8252-24QC AT89S8252-24AI AT89S8252-24JI AT89S8252-24PI AT89S8252-24QI AT89S8252-33AC AT89S8252-33JC AT89S8252-33PC AT89S8252-33QC Package 44A 44J 40P6 44Q 44A 44J 40P6 44Q 44A 44J 40P6 44Q 44A 44J 40P6 44Q Operation Range Automotive (-40C to 105C)

24

4.0V to 6.0V

Commercial (0C to 70C)

4.0V to 6.0V

Industrial (-40C to 85C)

33

4.5V to 5.5V

Commercial (0C to 70C)

= Preliminary Information

Package Type 44A 44J 40P6 44Q 44 Lead, Thin Plastic Gull Wing Quad Flatpack (TQFP) 44 Lead, Plastic J-Leaded Chip Carrier (PLCC) 40 Lead, 0.600" Wide, Plastic Dual Inline Package (PDIP) 44 Lead, Plastic Gull Wing Quad Flatpack (PQFP)

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