Cutler-Hammer D320 PLC, User Manual

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D320 PLC User's Manual
Communication Rules
Communication Environment
The D320 PLC communications protocol uses the following settings:
•
Half Duplex Asynchronous
•
No Parity
•
1 Stop bit
•
Communication method: RS232C, or RS485
•
Communication speed: 9600, 19200, or 38400 bps
•
Communication cable: Refer to the cable configuration in Chapter 4.
•
Number of PLCs on a single network: Maximum of 64 (communicating 1:N using RS485)
•
Maximum communication delay time: 3 sec
Communication Protocol
Step 1

 

Query (Q)
Set the network ID number for the PLC to communicate with and send a Q signal from the peripheral
device to the PLC.
Step 2
   
Query Acknowledge (QA)
A QA signal is sent from the PLC to the peripheral device, indicating that the Q signal from the
peripheral device was received.
Step 3

 

Response Request (RR)
An RR signal goes from the peripheral device to the PLC, indicating that the QA signal from the PLC
was received, and requesting the final data response. This signal is sent when Q
→
QA is normal.
Step 4

 

Response (R)
When the PLC receives the RR from the peripheral device, it sends an R signal which gives the results
of the original Q signal sent by the peripheral device. The communication cycle for one function code
ends when the PLC sends the R.