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CN3800 Series
Protocol Manual for
RS232C / RS422A

[1] Introduction ...3

[2] Specifications ...4

[3] Connection ...5
1. RS232C ...5
2. RS422A ...6

[4] Setting Requirements for Communication ...7
1. Communication Parameter Setting ...7
2. Operation Mode Setting ...8

[5] Communication Check ... 10
1. Preparation ... 10
2. Circuit Check ... 10
3. Poor Connection ... 11

[6] Establishment and Abandonment of Data Link ... 12
1. Establishment of Data Link ... 12
2. Abandonment of Data Link ... 13

[7] Communication Format ... 13
1. READ Command Format ... 13
2. WRITE Command Format ... 14
3. Control Codes ... 14
4. Check Code ... 14
5. Positive Acknowledgment and Negative Acknowledgment ... 15
6. Time Out, Etc. ... 16
[8] Details of Communication Commands ... 17
1. Common Specifications ... 17
2. Operation Mode Related Commands [01] ... 27
3. Display (LED) Related Commands [D1~D4] ... 28
4. Monitor Screen Related Commands [M1~M3] ... 30
5. Execution Parameter Screen Related Commands [E1~E5] ... 32
6. Program Data Screen Related Commands [P1, S1~S6] ... 34
7. Control Data Screen Related Commands [C1~C3] ... 37
8. KEY Lock Screen Related Commands [K1~K3] ... 38
9. Initial Data Screen Related Commands [I1~I9] ... 39

[9] Appendices ... 45
1. ASCII Code Table ... 45
2. Circuit Check Sample Program ... 46

[1] Introduction

The operating instructions in this copy describe the communication interface which is an

optional function prepared for the Program Controller CN3800 Series. For the functions

and features of the controller unit itself, refer to the Operating Instructions of the

controller unit.

Two types of communication interfaces, RS232C and RS422A, are available. By using

the types of signals conforming to the specifications of EIA RS232C or RS422A, various

types of data can be set or read from the CN3800 Series by personal computer, etc.

(Note: With the initial data screens, data can only be read but cannot be set or changed.

Data setting and changing are to be done by the LOC mode (front key).)

RS232C and RS422A are data communication standards specified by the U.S. Electronic

Industries Association (EIA). The Japanese standard corresponding to these standards is

JIS X5l01 (Old JIS C6361). This standard covers the electrical and mechanical points; in

other words, it refers to only the hardware. It does not touch upon the software aspect of

data transmission

procedures. Therefore, communication cannot be carried out unconditionally by a device
equipped with this interface. Users are required to be fully informed, in advance, of the
specifications and transmission procedures.

The use of RS422A allows parallel connection of multiple CN3800 Series Controllers (including
the Digital Controller SR25 Series). At present, only a few personal computers can support this
interface. However, the use of a line converter for FS232C/PS422A conversion solves the

[2] Specifications

Signal level: Conforming to EIA RS232C/RS422A

Communication mode: RS232C 3-wire half duplex
RS422A 4--wire half duplex multidrop

Synchronization system: Start--stop synchronization

Communication distance: RS232C l5m
RS422A 1.2km

Transmission speed: 1200, 2400, 4800 bps

Transmission procedure: Non-procedural

Data format: Data length 7 bits, even parity, stop bit 1


data length 8 bits, no parity, stop bit 1.

BOC: Checksum 1 byte
Communication codes: ASCII codes
Control codes: Not used.

Number of connectable units: RS232C 1 unit
RS422A 10 units

[3] Connection

1. RS232C

Example 1
Host computer CN3800

(1) Ground Ground (1)

(2) SD RD (3)

(3) RD SD (2)

(7) SG SG (7)

(4) RS >

(5) CS <

(20) ER >

(6) DR <

Example 2

Host computer CN3800
Shield (1)

SD RD (3)

RD SD (2)

SG SG (7)

RS >-----

DR <-----

CD <-----

ER <-----

CS <-----

2. RS422A

Example 1

Host computer CN3800
Shield (1)





SG SG (5)

Note: The figures in ( ) are Pin Nos.

* Return of the control signals shall be executed in accordance with the respective host
computer specifications.

Connector Pin Positions

[4] Setting Requirements for Communication

1. Communication Parameter Setting

The following communication parameters shall be set by displaying the Communication Option
Screen of the initial data screen. (Parameter setup or parameter alteration is not possible, though
monitoring is possible, unless the operation mode is set at "LOC" and the action mode is at
"RST" or "MAN" at the same time.)

(1) ADDR (Address ) Setting

Designate any number from 0 to 31. If multiple units are used,
designate different addresses for the various units. Be sure not to
designate the same number to more than one unit.

(2) BPS (transmission speed) setting

Designate any level from 1200, 2400, and 4800 bps to meet the
transmission speed of the host computer. If multiple units are used,
set them all at the same speed.

(3) DATA (Data bit length, parity) setting

Select the data bit length, parity, stop bit length from the following, to be set in
conformity with the host computer.

0: Data 7 bits, even parity, stop bit 1
1: Data 8 bits, no parity, stop bit 1

If multiple units are used, set them all with the same values.

2. Operation Mode Setting

Three types of CN3800 operation modes, as shown below, are available. Each
mode has a different communication condition.

1. LOC mode (Data setting is executed by operating front keys.)

2. EXT mode (Data setting is executed by external control input "DI".)

3. COM mode (Data setting is executed through communication system.)

[COM-EXT mode (Data setting is executed by external control input
during COM mode) ]

(1) During LOC or EXT mode, a data link can be established. However, [D1 ~ D4] READ
commands only are valid during COM mode and the error message "ERO" + NAK is
returned when any other command is delivered.

(2) During COM (COM-EXT) mode, all READ and WRITE commands are valid.

(3) To alter the operation mode, display the LCD operation mode screen and select/set LOC,
EXT or COM as required. Select for the operation of CN3800 by means of the
communication system.

*Refer to the Operating Instructions of the CN 3800 unit.

(4) If the input type, range, unit, or scaling is changed, or memory initialization (1,2) is executed
on any of the initial data screens during LOC mode, the CN3800 controller automatically
suspends the communication and abandons the data link, to enter Link-OFF status. Carry out
data link establishment again after a lapse of 500 msec.

[5] Communication Check

1. Preparation
(1) Connection

Referring to section [3] above, connect CN3800 to the host computer or the line

(2) CN3800 side preparation

ADDR (Address): 0

BPS (speed): 1200 bps

DATA (Data bit length): 7 bits, even parity

In addition to the above, change the operation mode from LOC to COM mode.

(3) Host computer side preparation

The setting contents shall be the same as the CN3800 side.

2. Circuit Check
Install the sample program presented at the end of these instructions in
the host computer, and run the program. This program is a sample
prepared for NEC PC-9801 Disk Basic N88-BASIC (86). If
using another model, OS, or language, the user must prepare an equivalent

When the program is run and the following display is given, the circuit connection can be judged
as correctly arranged. The values represent PV value, SV value, PTN no., STP no., as in the


Dl 23.5, -- ,l, l


The PV value above changes with measuring range, measuring temperature, or other condition.

3. Poor Connection

If the above circuit check does not operate normally, check again for poor connection
with the host computer, faulty setup, or the program itself. In particular, it should be
noted that the wiring specification for the return line of the control signal wire on the
host computer side differs from one type of host computer to another.

[6] Establishment and Abandonment of Data Link

If a data link is not yet established CN3800 does not process or return the data

even if receiving a READ command or WRITE command. Never fail to send out

command(s) after establishing the data link.

1. Establishment of Data Link

Master station (Host) Slave station CN3 800


"ADDR" + ACK (Normal)
No response (Abnormal)

In the case of "ADDR (Address) No. = 10", four bytes of

04H + 31H + 30H + 05H are transmitted.
(EOT) (1) (0) (ENQ)

(l) CN3800 with the data link established by ECT is linked off.

(2) With a normal response given, reading or changing of the CN 3800
data by the READ command and WRITE command can be executed.
(3) The two-digit no. 0031 set on CN3800 side shall be designated to the address no.

(4) There is no response from CN3800 if there exists no CN3800 with the
specified address no. or if no normal receive operation is performed.

2. Abandonment of Data Link
Master station (Host) Slave station CN3800

EOT No response

(1) Transmission of ECT links off the CN3800 with data link established.

[7] Communication Format

1. READ Command Format

The READ command reads the data, status, etc., of CN3800

Master station (Host) Slave station CN3800


(Data Request) "ER*" + NAK (Abnormal)

(Abnormal) STX + "TEXT" + ETX +
BCC (Normal)

NAK ------------- (Max. 3 times)

2. WRITE Command Format

The WRITE command sets up (or alters) the data, execution keys, etc., of

Master station (Host) Slave station CN3800
(Data setup) ACK (Normal)
"ER*" + NAK (Abnormal)

3. Control Codes

The following control codes are used.

STX : 02H ETX : 03H

ECT : 04H ENQ : 05H

ACK : 06H NAK : 15H

4. Check code

(1) Checksum is employed as a check code (BCC).

(2) The BCC range is from immediately after STX to ETX. In other words, all the data
placed after ETX are considered BCC data.

(3) Addition of the various ASCII data within the above mentioned valid range is made
ignoring the carry at the most significant bit.

Example: In case of READ command for the monitor screens

STX + "M1" + ETX + BCC

(02H) (4DH) (31H) (03H) (81H)

4DH + 31H + 03H = 81H (8 bits)

( 81H & 7FH = 01H (7 bits) )

5. Positive Acknow1edgment and Negative Acknow1edgment

(1) ACK is returned at a positive acknowledgement (when data is normally received).

(2) Error message ("ER*") added before NAK is returned as a negative acknowledgement
(when data is abnormally received). (* : 0 ~ 6) A detailed description of the error
message is given in [8]