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Contents
DATA COMMUNICATIONS. . 12-1 Error Conditions . 12-54
INTRODUCTION 12-1 Adapter Check 12-54
Data Communications Systems 12-1 Data Set (Not) Ready 12-55
Data Communications Networks . 12-1 Abortive Disconnect . 12-55
Point-to- Point Network . . . 12-1 Receive Time-out . 12-55
Multipoint Network . . . . . 12-1 Invalid ASCII Character 12-55
Binary Synchronous Communications 12-2 Invalid Frame . 12-55
BSC Message Format . . . . . . 12-2 Secondary SDLC Time-out (Inactivity
Transmit and Receive Storage Contents of Timer) 12-55
Message . . . . . . . . . . . . . . 12-4 Primary SDLC Time-out (Idle Detect)
EBCDIC, ASCII, and Line Control Characters 12-5 and Nonproductive Timer) . 12-55
Synchronous Data Link Control 12-6 Block/Frame Check Error 12-55
Frame Format . . . . . . . . . . . . . 12-6 DBO Parity . 12-55
Control Field Formats . . . . . . . . . . 12-7 Diagnostics . 12-56
Primary Station Commands and Secondary Diagnostic Mode and Wrap Test 12-56
Station Responses . . . . . . . . . . . 12-8 Internal Clock Feature 12-60
Examples of SDLC Commands and Responses 12-9 EIA/CCITT Line Adapter 12-61
Systems Network Architecture 12-10 MODEMS 12-62
SNA/SDLC Data Relationship 12-10 IBM 1200 BPS Integrated Modem 12-62
Types of Network Addressable Units 12-10 Nonswitched Network Interface . 12-62
Physical Configuration 12-10 Switched Network Interface 12-64
SNA/SDLC Buffer 12-12 1200 BPS Transmit Operations 12-66
Modems and Interfaces 12-19 Receive Operations 12-66
COMMUNICATIONS ADAPTER 12-20 Automatic Answering 12-66
Data Flow 12-20 1200 BPS Integrated Modem Tests 12-67
Functional Units . . . 12-21 Line Plate for Public Switched Network 12-68
Adapter Controls . 12-24 IBM 2400 BPS Integrated Modem 12-68
System Level Interface 12-28 Operation 12-68
Queue . . . . . . 12-28 2400 BPS Transmit Data Flow 12-72
Input/Output Blocks. 12-28 2400 BPS