Rockwell Automation 1769-HSC Compact High Speed Counter Module - Manual (Page 30)

30 Rockwell Automation Publication 1769-UM006E-EN-P - July 2013
Chapter 2 Module Operation
Counter Enable/Disable
The counter can be enabled or disabled using the Ctr
nEn control bit. Be aware
that disabling the counter does not inhibit any current count loading functions
(for example, preset or direct write) or any Z function.
Z Input Functions
There are three Z input functions: store, gate, and Z preset.
Store
The Z-input can be used to capture the current count value even when the
counter is counting at full 1 MHz speed.
Gate
The Z-inputs can be used to gate (hold) the counter at its current value regardless
of incoming A or B inputs. A gating function is typically one that lets pulses reach
the counter (gate open) or not (gate closed).
Z Preset
Preset can be programmed to occur based on the actions of the Z-input signal.
Inhibit and Invert
The Z-input signals can be inverted and/or inhibited, depending on the user
configuration of the Ctr
nZInvert and CtrnZInhibit output control bits. If the
signal is inhibited, the invert bit is the Z signal for the actions described above.
For an explanation of those bits, see Z Inv - Z Invert (CtrnZInvert) on page 93
and Z Inh - Z Inhibit (CtrnZInhibit) on page 93 .
Direct Write
You can arbitrarily change the current count value (Ctr[
n].CurrentCount) to the
direct write control value (Range12To15[
n].HiLimOrDirWr). This ability
applies to ranges 12…15. The direct write value takes effect when the Load Direct
Write bit (Range12To15[
n].LoadDirectWrite) transitions from 0 to 1.
If you attempt to preset and load direct write to a counter at the same time, only
the preset (Ctr
nPreset) will take effect.