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kb:production:s7-communication:iso-tp

03 ISO TP

aka COPT

Name ISO Transport Protocol
ISO ISO DP 8073
RFC RFC 905

The COTP packet is the content (the TPDU) of the TPKT packet. The structure of the packets depends on the type of data sent.

Connection Request

Packet Structure
ISO TP PDU
ISO on TCP TPKT TPDU
Contents
Byte Value Description
Fixed part
[0] 0x11 LI (Length Indicator): Length of Header (17)
[1] 0xE0 bits 1-4: PDU Type Specification (1110 = CR)
bits 5-8: Credit (0000 = non-reliable)
[2-3] 0x00 00 DST - REF
[4-5] 0x00 01 SRC - REF (can be set by the client)
[6] 0x00 CLASS (Class/Extended Format/Flow Control)
Variable part
TPDU Size parameter
[7] 0xC0 param code = 0xC0
[8] 0x01 param length = 0x01
[9] 0x09 param value: Size (512 = 0x09; 1024 = 0x0A)
Calling (Src) TSAP parameter
[10] 0xC1 param code = 0xC1 (calling TSAP)
[11] 0x02 param length = 2 bytes
[12] 0x01 param value: Device Group (PG/PC = 0x01)
[13] 0x00 param value: TSAP ID (eg 0x00)
Called (Dst) TSAP parameter
[14] 0xC2 param code = 0xC2 (called TSAP)
[15] 0x02 param length = 2 bytes
[16] 0x03 param value: Device Group (OP = 0x02; Others = 0x03)
[17] 0x…… param value: Slot [bits 0..4] and Rack [bits 5..7] Numbers (see PLC Types)

Data Transfer

Packet Structure
ISO TP Header User Data
ISO on TCP TPKT TPDU
Byte Value Description
Fixed part
[0] 0x02 LI (Length Indicator): Length of Header (2)
[1] 0xF0 bits 1-4: PDU Type Specification (1111 = DT)
bits 5-8: Credit (0000 = non-reliable)
[2] 0x80 bits 1-7: TPDU-NR (0)
bit 8: End-Of-Traffic (1)
User Data

aka S7 PDU

See 04 S7 Comm.

kb/production/s7-communication/iso-tp.txt · Last modified: 2019/12/10 10:29 by joerg.hampel