Operating Modes; Counter Mode - Allen-Bradley 1734-IJ User Manual

1-2 About the Modules

Operating Modes

Publication 1734-UM006B-EN-P - August 2005
The encoder/counter modules operate in the modes shown in the
table.
Mode

Counter Mode

Encoder Mode
Period/Rate Mode
Rate Measurement Mode
The operation of the counter and encoder modes is nearly identical.
The difference between the two modes is in the type of feedback (1
phase versus 2 phase) for the count direction (up or down).
• In encoder mode, a transition is expected on B for counting to
proceed in a direction.
• In counter mode, the B input may be left at a static level.
Select operating modes by writing appropriate configuration data to
the module.
Counter Mode
The counter mode reads incoming pulses and returns a binary number
(0 - 16,777,215 ) to the POINTBus. The counter mode only accepts
max
single phase inputs. The module determines the Phase B input state,
and counts up or down accordingly.
Channel A input is used as the counting pulse while channel B is used
to determine the direction.
[B = High, Count = Down; B = Low or floating (not connected), Count
= Up]
The Channel B input may be tied high or low for unidirectional
counting, or toggled for bidirectional counting.
Description
Read incoming single phase pulses, return a binary
count
Read incoming 2 phase quadrature pulses, return a
binary count
Count internal clocks during the On period, return a
frequency
Read pulses during the sample period, return a
frequency