Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 70)

Chapter 5
Developing Programs
5-10
For example, a PLC-5 programmable controller initiates an unsolicited
READ MSG instruction to the control coprocessor. The READ MSG
instruction transfers one word of data. The order of events is:
The control coprocessor program
responds with a
MSG_READ_HANDLER or
MSG_READ_W_HANDLER
then
The MSG_READ_HANDLER or
MSG_READ_W_HANDLER triggers
a DTL_WRITE in the program, based
on the one word that was sent
Note: The DTL_WRITE function writes data from the
control coprocessor to the PLCĆ5 programmable controller.
Check Status of Asynchronous MSG Functions (MSG_WAIT)
When your application program uses asynchronous MSG read/write
functions, you must include at least one MSG_WAIT in your program.
MSG_WAIT checks for the completion of any combination of pending
read/write message number and updates the message number in a read
and write mask.
Mask Functions
Use the MSG_ZERO_MASK function to zero all the bits in a mask from
previous operations when you use a MSG_WAIT function in your
program. All the mask functions are used with the MSG_WAIT function.
Table 5.H
Mask Functions for Unsolicited, Asynchronous Read and Write Functions
Function What It Does
MSG_CLEAR_MASK Clears the bits in the message read/write masks associated with a specified message number
MSG_SET_MASK Sets the bits in the message read/write masks associated with a specified message number
MSG_TST_MASK Tests the bits in the message read/write masks associated with a specified message number
MSG_ZERO_MASK Used to zero all the bits in a specified message number
Clear Pending Messages
See page 5-13 for information on using the CC_MKILL utility to clear
pending messages from the message handler.
TAG functions provide a means for the user to specify access to control-
coprocessor memory. Use TAG functions to access memory for:
external intelligent devices—i.e., ControlView connected to a serial port
multiple processes interacting on OS-9
You can configure the size of the TAG table using the CC_CFG utility.
The default size allows the creation of 1024 TAGs.
How to Use TAG Functions