Cancel Commreq Function (4399) - GE PACSystems RX7i Reference Manual

Chapter 6. Serial I/O, SNP & RTU Protocols

6.2.11 Cancel COMMREQ Function (4399)

This function cancels the current operations in progress. It can be used to cancel both read operations
and write operations.
If a read operation is in progress and there are unprocessed characters in the input buffer, those
characters are left in the input buffer and available for future reads. The serial port is not reset.
Example Command Block for the Cancel Operation Function
Value
(decimal)
Address 0002
Address +1 0000
Address +2 0008
Address +3 0000
Address +4 0000
Address +5 0000
Address +6 4399
Address +7 0001
Operating Notes
Remote COMMREQs that are cancelled due to this command executing will return a COMMREQ status
word indicating request cancellation (minor code 12H).
218
Value Meaning
(hexadecimal)
0002 Data block length (2)
0000 NOWAIT mode
0008 Status word memory type (%R)
0000 Status word address minus 1 (%R0001)
0000 Not used
0000 Not used
112F Cancel operation command
0001 Transaction type to cancel
If this COMMREQ is sent in either Cancel All or Cancel Write
mode when a Write Bytes (4401) COMMREQ is transmitting a
string from a serial port, transmission is halted. The position
within the string where the transmission is halted is
indeterminate. In addition, the final character received by the
device to which the CPU is sending is also indeterminate.
PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual
1 - All operations
2 - Read operations
3 - Write operations
Caution
GFK-2222AD