Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module - Manual (Page 22)

Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
22 Counter Modes
Preset
Each of the two counters has one preset value associated with it. In the
Encoder or Counter modes, the preset value represents a reference point (or
value) from which the module begins counting. The module can count either
up or down from the preset value.
The preset value itself is entered during module configuration. However, you
must enter a preset command from either the RSLogix 5000 programming
software or ladder logic before it becomes active. Setting the Preset Enable Bit
in the Output tag to ‘1’ will send the preset value to the Present Value tag.
Preset values are entered on the Counter Configuration tab of the Module
Properties dialog box.
See page 65 for an example of the Counter Configuration tab.
Preset in Output tag
When using the HSC Data-extended Comm Format while configuring the
module, the Preset tag will be found in both the Configuration and Output tag
areas.
The Configuration tag value is populated during software configuration with
the Logix5000 controller, and sent to the module upon powerup, defining its
behavior. This value will continue to define module behavior as long as the
corresponding tag in the output area is zero.
If the value of the Preset tag in the output area is changed to a non-zero value,
the module will disregard the value sent from the configuration area and use
the value in the output area instead. This facilitates easier real-time ‘on-the-fly’
changes to the preset function.
Rollover
Each of the two counters has one rollover value associated with it. When the
accumulated count value in the Rollover tag reaches the rollover value, it resets
to zero (0) and begins counting again. The rollover value is circular (for
example, if the rollover value = 360, the count will be from 358, 359, 0, 1, and
so forth, in a positive direction and from 1, 0, 359, 358, and so forth, in a
negative direction).
Rollover values are entered on the Counter Configuration tab of the Module
Properties dialog box in the RSLogix 5000 programming software or can be
changed in ladder logic.
See page 65 for an example of the Counter Configuration tab.