Rockwell Automation 1746-HSCE2 Multi-Channel High Speed Counter Module - Manual (Page 28)

Publication 1746-UM002B-EN-P - August 2004
2-8 Module Operation
Gate and Preset Limitations
Because only the Z inputs are used for external gating and presetting,
the only gate/preset modes available for Counters 3 and 4 are No
Preset and Soft Preset Only. All six modes are always available for
Counters 1 and 2.
Gate and Preset Considerations
Z-pulse Preset Operation
In applications where the Z pulse of the encoder is being used to
preset the position, and where the Z pulse of the encoder is aligned
with either the A or B pulses, the capture or count value may be
affected by ± 1 count. If the Z pulse is edge aligned with the A pulse,
preset operations may not be performed accurately in any of the
quadrature modes. If the Z pulse is edge aligned with the B pulse,
preset operation may not be performed accurately in the X4
quadrature mode only. A small capacitor (for example, 0.01 µF) across
the Z inputs will dis-align these inputs and should correct this
condition.
Summary of Available
Counter Configurations The table below summarizes the input configurations and gate/preset
modes available for all counters, based on operating mode.
IMPORTANT
In Class 1, Operating Mode 2, Counter 2 does not
have a capture value available. In Class 1, Operating
Mode 3, no capture values are available.
Operating
Mode Counter Input Configuration Gate/Preset Mode
1 1 All All
2 All All
2 1 All All
2 Pulse/Internal Direction All
3 Pulse/Internal Direction No Preset or Soft Preset Only
3 1 Pulse/Internal Direction All
2 Pulse/Internal Direction All
3 Pulse/Internal Direction No Preset or Soft Preset Only
4 Pulse/Internal Direction No Preset or Soft Preset Only