Rockwell Automation 1775-S5_SR5,D17756.5.5 User Manual PLC-3 FAMILY I/0 - Manual (Page 131)

Binary Command Language
Appendix A
A-3
Response Timeout (Master waiting for response block after ACK)
A response timeout occurs when the scanner does not send a response
block back to the master within a given time after acknowledging receipt
of a command block.
The master device determines the time allowed ( the scanner is not aware
of this timeout). Typically, a one minute response timeout provides
enough time for the scanner to respond without unnecessarily slowing the
master device.
After a response timeout, the master device:
sends a CCR to the scanner
checks the protocol fault code in the CCR response (refer to Table A.A)
If the fault code is: The master device:
00 hex (no fault) or 05 hex (no input buffer
available)
clears its error count and retransmits the
last block.
another fault code (besides 00 or 05 hex) or
if the scanner does not respond to the CCR
within one character timeout period
terminates communication or tries to
reĆinitialize communication.
Acknowledge Timeout (Master or scanenr waiting for ACK)
The maximum amount of time the scanner waits for an ACK, NAK, or SO
from the other device after sending a response or command is 2 seconds
(S4A used character timeout value). Master must also select a value for
this timeout.
This timeout should be treated as if a NAK were received. The driver stops
transmitting for one character timeout value and then reissues the
command or response.