Publication 1763-RM001B-EN-P - April 2007
Communications Instructions
345
Channel Select
When using the SVC instruction, you must select the channel to be
serviced. The channel select variable is a one-word bit pattern that
determines which channel is serviced. Each bit corresponds to a specific
channel. For example, bit 0 equals channel 0. When any bit is set (1), the
corresponding channel is serviced.
Communication Status Bits
The following communication status bits allow you to customize or
monitor communications servicing. See General Channel Status Block on
page 58 for additional status information.
Application Example
The SVC instruction is used when you want to execute a communication
function, such as transmitting a message, prior to the normal service
communication portion of the operating scan.
Controller
Channel Select Setting Channel(s) Serviced
MicroLogix 1100
1h
0
2h
1
3h
both
Communication Status Bits
Address
Description
Channel 0
Channel 1
CS0:4/0
ES:4/0
ICP - Incoming Command Pending
CS0:4/1
ES:4/1
MRP - Incoming Message Reply Pending
CS0:4/2
ES:4/2
MCP - Outgoing Message Command Pending
CS0:4/4
CAB - Communications Active Bit
0000
CS0:4
MCP
SVC
Service Communications
Channel Select
0001h
SVC
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