Cutler-Hammer D320 PLC, Руководство пользователя

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Appendix A: D320 PLC Communication Protocol
205
Read Bits
The following can be read:
•
Bits stored in the absolute address (R, L, M, K, or F).
• N consecutive bit contents (On/Off).
Query (Q) frame
Response (R) Frame
Number of bits to be read
Absolute bit address
(address of first bit to read)
For example:
K127.12 (address K127’s 12th bit)
Absolute bit address = $1BFC
Length of
information (bit)
Function Code
Peripheral Device
ID (PC ID)
PLC ID (CPU ID)
Base CRC
DA SA $01 $03 L H N L H
Bits that are On are represented by the
one byte value $FF. Bits that are Off have
a value of $00.
Length of information (number of bytes)
from the length to the next CRC.
Response code ($80 added to the
original function code).
PLC ID (CPU ID)
Peripheral Device ID (PC ID)
For the response, the PLC is the sender
and the PC the receiver, so the DA and SA
are reversed from the Q message.
DA SA $81 N Bit value Bit value … Bit value L C
Base+0 Base+1 Base+N-1 CRC