Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module - Manual (Page 21)

Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
Counter Modes 21
Encoder x4
Encoder x4 mode is identical to x1, except this mode counts on the leading
and trailing edges of A and B to provide a greater number of pulse counts. The
greater the number of pulse counts the better the module can
determine position.
Input Z is used in Encoder mode only if a Store Count mode is enabled.
See
page 23 for details on the storage modes.
Encoder x4 Mode
Maximum frequency in Encoder x1 and x4 modes = 250 kHz (assuming
50% duty cycle), with a minimum pulse width at this frequency of 2 s. The
module assumes a 90° phase (A/B°) difference between channels.
Input A
Quadrature Encoder
1756-HSC Module
Input B
Input A
Input B
Input A
Input B
B Leads A 90° A Leads B 90°
1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 0
41689
Accumulated Count
in Present Value Tag
Directional Frequency
in Totalizer Tag
Positive Frequency Negative Frequency
Input Z (optional)