Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 224)

API Library of Routines
Appendix B
MSG_READ_HANDLER
B-93
BASIC Example
The BASIC function code is 41.
DIM status : INTEGER
DIM iostat : INTEGER
DIM msgrbuf(5) : INTEGER
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rem * MSG_READ_HANDLER - Set up handler to allow for an asynchronous message
rem * read of msgrbuf. This function will return to the
rem * user before completion of the I/O. MSG_WAIT must be
rem * called to complete the I/O process. Size of buffer
rem * is 20 bytes, message number is 0, number of items to
rem * read is 5, the timeout value is 6 seconds, the
rem * coprocessor data type is integer, the plc data type
rem * is short and iostat gets the I/O completion code.
RUN AB_BAS (41,status,ADDR(msgrbuf(1)),20,0,5,6,5,3,ADDR(iostat))
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References
MSG_WRITE_HANDLER(); MSG_WAIT(); MSG_CLR_MASK();
MSG_SET_MASK(); MSG_TST_MASK(); MSG_ZERO_MASK();
Also see synchronous functions:
MSG_WRITE_W_HANDLER(); MSG_READ_W_HANDLER();