Revolution Counter - NXP Semiconductors freescale KV4 Series Reference Manual

Chapter 41 Quadrature Encoder/Decoder (ENC)
41.2.7 Position Difference Counter
The 16-bit position difference counter contains the position difference value occurring
between each read of the position register. This register counts up or down on every
count pulse. The counter acts as a differentiator whose count value is proportional to the
change in position since the last time the position counter was read. When the position
register, the position difference counter, or the revolution counter is read, the position
difference of the counter's contents is copied into the position difference hold register
(POSDH) and the position difference counter is cleared.
41.2.8 Position Difference Counter Hold
This register stores a copy of the position difference counter at the time the position
register was read. When the position register is read, the position difference of the
counter's contents is copied into the position difference hold register (POSDH) and the
position difference counter is cleared.

41.2.9 Revolution Counter

The 16-bit up/down revolution counter is intended to count or integrate revolutions by
counting index pulses. The direction of the count is determined by the Count_Up and
Count_Down signals, determined by the Phase A and B inputs. A different count
direction on the rising and falling edges of the index pulse indicates the quadrature
encoder changed direction on the index pulse.
41.2.10 Pulse Accumulator Functionality
The logic can be programmed to integrate only selected transitions of the PHASEA
signal. In this way the position counter is used as a pulse accumulator. The count
direction is up. The pulse accumulator can also optionally be initialized by the INDEX
input.
KV4x Reference Manual, Rev. 2, 02/2015
Preliminary
Freescale Semiconductor, Inc. 1043