Rockwell Automation Allen-Bradley ControlLogix 1756-MVI Programming Reference Manual page 38

3-16 MVI Backplane API
Publication 1756-RM004B-EN-P - October 2000
MVIbp_SendMessage
Syntax:
int MVIbp_SendMessage(MVIHANDLE handle, WORD *buffer,
WORD length, WORD reserved, WORD timeout);
Parameters:
handle handle returned by previous call to MVIbp_Open
buffer pointer to buffer of data to send to processor
length the length in words of the message to send.
reserved must be set to 0
timeout maximum number of milliseconds to wait for processor to
read message
Description:
This function sends a message to the control processor. handle must be
a valid handle returned from MVIbp_Open.
Upon calling this function, length should contain the message size in
words. buffer must point to a buffer of at least length words in size.
If length exceeds the maximum message size specified by the value
MsgSndBufSize (see the MVIbp_SetIOConfig function),
MVI_ERR_BADPARAM will be returned.
reserved is not used for the 1756-MVI module and must be set to zero.
MVI_ERR_BADPARAM will be returned if reserved is not zero.
timeout specifies the number of milliseconds that the function will wait
for the message to be transferred to the control processor. If the timeout
occurs before the message has been transferred, MVI_ERR_TIMEOUT
will be returned.
If timeout is 0, the function will return immediately. If the message was
successfully queued to be sent, MVI_SUCCESS will be returned. If the
message was not queued (e.g., no resources were available to queue
the message), MVI_ERR_TIMEOUT will be returned and the message
must be re-tried at a later time. A timeout of 0 allows an application to
perform other tasks while the message is being transmitted.