Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module - Manual (Page 104)

Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
104 1756-HSC Module History
Change Configuration
Data via Message
Instruction
Ladder logic uses message instructions to change the module configuration
during module operation for software versions 15 and earlier. Message
instructions maintain the following characteristics:
• Messages use unscheduled portions of system communication
bandwidth
• One service is performed per instruction
• Performing module services does not impede module functionality, such
as counting incoming pulses
Because message instructions use unscheduled portions of systems
communication bandwidth, the services requested of a 1756-HSC module are
not guaranteed to occur within a specific time period. Although the module
response typically occurs in less than a second, there is no specific time
interval that reflects this response.
Message instructions cause a module service to be performed only once per
execution. For example, if a message instruction sends new configuration data
to the module, the message instruction must be re-executed to update and
send the configuration data in the future.
For procedures, see the Logix5000 Controllers Messages Programming
Manual, publication
1756-PM012 .