Hardware reference guide

Intelligent/Special Purpose
35013379 11/2011 321
I/O Configuration for 140EHC20200
Overview
This section describes configuration of the 140EHC20200 high speed counter
module which operates in pulse or quadrature mode and accepts single ended or
differentiated inputs.
I/O Map Register Assignment
The 140EHC20200 high speed counter requires six contiguous output (4X) and six
contiguous input (3X) registers in the I/O map.
The 4X registers perform the same configuration tasks as the Modzoom screen-
assigned parameters. Also, the preset and the enable inputs connected to the field
wiring terminal block perform the same functions as those software command
control bits. When both methods are used to:
z Preset a counter—the last preset executed has precedence.
z Enable/disable a counter—it will only be enabled when both the hardware enable
input and software enable control bit are in the enable state.
For simple applications, the zoom screens rather than the I/O mapped registers can
be used to configure the module. Zoom screens are used only while the PLC is
stopped. The selected parameters take effect when the PLC is set to run. For
applications that require that module parameters be changed while the system is
running, user logic can modify the I/O map-assigned registers to override the
previously selected zoom parameters.
When using either zoom screens or I/O map registers, the maximum values
specified in the Load Values Command section are the largest values that can be
used by the module.
The I/O Mapped registers discussed in this section are
4x output registers that:
z Preset and enable/disable input counters.
z Load setpoint and maximum values to define output turn on points.
z Set mode of operation, count, or rate sample.
z Enable output switches and configures their mode of operation.