Calling Serial I/O Commreqs From The Plc Sweep; Compatibility; Status Word For Serial I/O Commreqs - GE VersaMax PLC User Manual

12.3 Calling Serial I/O COMMREQs from the PLC Sweep

Major Error
Code
1 (01h)
12 (0Ch)
Serial I/O / SNP / RTU Protocols
For public disclosure
Implementing a serial protocol using Serial I/O COMMREQs may be restricted by the
PLC sweep time. For example, if the protocol requires that a reply to a certain message
from the remote device be initiated within 5mS of receiving the message, this method
may not be successful if the PLC sweep time is 5mS or longer, since timely response is
not guaranteed.
Since the Serial I/O is completely driven by the application program, in STOP mode a
port configured as Serial I/O automatically reverts to SNP slave, to facilitate programmer
communication. Therefore, while in Stop mode, Serial I/O protocol is not active; it is only
active when the PLC is in Run mode.
When the port reverts back to SNP Slave, the same serial communications parameters
(baud rate, parity, stop bits ...) as the currently-active Serial I/O protocol are used.
Therefore the programmer must use the same parameters for it to be recognized. If any of
the parameter values associated with the Serial I/O protocol are not supported by the SNP
Slave protocol, the programmer will not be able to communicate with the PLC via that
port.

12.3.1 Compatibility

The COMMREQ function blocks supported by Serial I/O are not supported by other
currently-existing protocols (such as SNP slave, SNP master, and RTU slave). Errors are
returned if they are attempted for a port configured for one of those protocols.

12.3.2 Status Word for Serial I/O COMMREQs

A value of 1 is returned in the COMMREQ status word upon successful completion of the
COMMREQ. Any other value returned is an error code where the low byte is a major
error code and the high byte is a minor error code.
Successful Completion (this is the expected completion value in the
COMMREQ status word).
Local error —Error processing a local command. The minor error code
identifies the specific error.
Wait-type command is not permitted. Use No-Wait
1 (01h)
command.
2 (02h) COMMREQ command is not supported.
5 (05h) Error writing COMMREQ status word to PLC memory.
6 (06h) Invalid PLC memory type specified.
7 (07h) Invalid PLC memory offset specified.
8 (08h) Unable to access PLC memory.
9 (09h) Data length exceeded.
12 (0Ch) COMMREQ data block length too small.
14 (0Eh)
COMMREQ data is invalid.
Description
GFK-1503E User Manual 233