Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 223)

API Library of Routines
Appendix B
MSG_READ_HANDLER
B-92
Returns
Status Symbolic Name Meaning
0 CC_SUCCESS Operation successful
133 CC_E_BAD_MSGID Message number invalid
157 CC_E_NOTCONNECT PLC is not connected or offline
160 CC_E_INV_TO Invalid timeout value
162 CC_E_INV_CTYPE Invalid coprocessor data type
163 CC_E_INV_PTYPE Invalid PLCĆ5 data type
181 CC_E_MSGPEND Message already pending
182 CC_E_MSG_ABORT Message aborted
190 CC_E_SIZE Invalid size for operation
191 CC_E_TOOSMALL Size of buffer too small
Description
Use the MSG_READ_HANDLER function to initiate the processing of
unsolicited message read instructions from the PLC-5 programmable
controller. This function puts an entry in the Message Control Table
(MCT) for the requested message number (0-31). When the PLC-5
programmable controller executes that message number, data from the
PLC-5 programmable controller is transferred to the specified user buffer.
This function is asynchronous. When this function is initiated, control is
returned to the application. Use MSG_WAIT to monitor/complete the I/O
operation. For the synchronous version of this command, see
MSG_READ_W_HANDLER.
C Example
See MSG_WAIT on page B-102 for a complete example of asynchronous
message processing.