Data Exchange Via Fetch Messages Involving 3964R With Rk512 - Pepperl+Fuchs IVI-KHA6-4HRX Manual

IDENT-I • IVI-KHA6-4HRX, IVI-KHD2-4HRX
Operating control interface units using the 3964R protocol
3.) With interpreter RK512, communication involving send-messages
host

8.1.4 Data exchange via FETCH messages involving 3964R with RK512

This type of data exchange is possible only in the basic fixed code operating mode.
The first time a FETCH message is received, the control interface unit switches into
a "Read" mode in which all read heads connected to the control interface unit are in-
terrogated continuously.
For each correctly received FETCH message, the control interface unit returns a re-
sponse message, in which the status of all 4 read heads (always 20 bytes) is trans-
mitted.There are 5 bytes for each read head. The data length for a read head is the
same whether or not a code has been read.
Each head has a "Read Sequence number" (8 bits) which is incremented whenever
• two codes are read in succession, and the first differs from the second
• two identical codes are read in succession, and the first of these has been trans-
mitted to the control system
Byte1...Byte5
Data, Head 1
Bild 8.3: Structure of message data
Subject to reasonable modifications due to technical advances.
38
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device
STX
DLE
Message head, command, DLE, ETX, BCC
DLE,
DLE
Response message head, DLE, ETX, BCC
DLE
STX
DLE
Message head, data, DLE, ETX, BCC
DLE,
DLE
Response message head, DLE, ETX, BCC
DLE
Byte6...Byte10 Byte11...Byte15
Data, Head 2
STX
STX
Byte16...Byte20
Data, Head 3 Data, Head 4
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