Rockwell Automation Allen-Bradley ControlLogix 1756-MVI Programming Reference Manual page 63

MVIcip_ReadConnected
Syntax:
int MVIcip_ReadConnected(
MVIHANDLE apiHandle,
MVIHANDLE connHandle,
BYTE *dataBuf,
WORD offset,
WORD dataSize );
Parameters:
apiHandle handle returned by previous call to MVIcip_Open
connHandle handle of open connection
dataBuf pointer to buffer to receive data
offset offset of byte to begin reading
dataSize number of bytes to read
Description:
This function is used by an application read data being received on the
open connection specified by connHandle. apiHandle must be a valid
handle returned from MVIcip_Open. connHandle must be a handle
passed by the connect_proc callback function. offset is the offset into
the connected data buffer to begin reading. dataBuf is a pointer to a
buffer to receive the data. dataSize is the number of bytes of data to be
read.
Notes:
When a connection has been established with a ControlLogix 5550
controller, the first 4 bytes of received data are processor status and are
automatically set by the 5550. The first byte of data appears at offset 4
in the receive data buffer.
A Run/Idle status word is appended when the communication format is
one of the "Data-xxx" types. This status word is not used for "Input
Data-xxx" types or status connections. Only the least significant bit of
the word is used. All other bits are reset to 0. When set to 1 (run), the
bit signals the module to activate its I/O. When reset to 0, it signals the
module to deactivate I/O (idle state).
The Run/Idle bit can be set only when the processor is in Run mode.
The bit is reset when the 5550 processor:
• goes into a major fault state
• is in program mode
• is in test mode
CIP Messaging API
Publication 1756-RM004B-EN-P - October 2000
4-11