Rockwell Automation 1734-IK Encoder/Counter Modules User Manual - Manual (Page 12)

Publication 1734-UM006B-EN-P - August 2005
1-2 About the Modules
Operating Modes The encoder/counter modules operate in the modes shown in the
table.
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
max
) to the POINTBus. The counter mode only accepts
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.
Mode Description
Counter Mode Read incoming single phase pulses, return a binary
count
Encoder Mode Read incoming 2 phase quadrature pulses, return a
binary count
Period/Rate Mode Count internal clocks during the On period, return a
frequency
Rate Measurement Mode Read pulses during the sample period, return a
frequency