41.5.1 Positive versus Negative Direction
A typical quadrature encoder has three outputs:
1. PHASEA signal
2. PHASEB signal
3. INDEX pulse (not shown)
If PHASEA leads PHASEB, then motion is in the positive direction. If PHASEA trails
PHASEB, then motion is in the negative direction. Transitions on these phases can be
integrated to yield position or differentiated to yield velocity. The quadrature decoder is
designed to perform these functions in hardware.
41.5.2 Prescaler for Slow or Fast Speed Measurement
For a fast moving shaft encoder, the speed can be computed by calculating the change in
the position counter per unit time, or by reading the position difference counter register
(POSD) and calculating speed. For applications with slow motor speeds and low line
count quadrature encoders, the timer module enables high resolution velocity
measurements by measuring the time period between quadrature phases. The timer
module uses a 16-bit free running counter operated from a prescaled version of the IPBus
clock. The prescaler divides the IPBus clock by values ranging from 1 to 128. A 60 MHz
IPBus clock frequency would yield a resolution of from 17 ns to 2.1 μs and a maximum
count period of from 1.09 ms to 140 ms. For example, with a 1000 tooth decoder, speeds
could be calculated down to 0.11 rpm using a prescaler.
41.5.3 Holding Registers and Initializing Registers
Hold registers are associated with three counters:
1. Position
2. Position difference
3. Revolution
Chapter 41 Quadrature Encoder/Decoder (ENC)
KV4x Reference Manual, Rev. 2, 02/2015
Freescale Semiconductor, Inc.
Preliminary
1061
Содержание freescale KV4 Series
Страница 2: ...KV4x Reference Manual Rev 2 02 2015 2 Preliminary Freescale Semiconductor Inc...
Страница 60: ...KV4x Reference Manual Rev 2 02 2015 60 Preliminary Freescale Semiconductor Inc...
Страница 82: ...JTAG Controller Configuration KV4x Reference Manual Rev 2 02 2015 82 Preliminary Freescale Semiconductor Inc...
Страница 88: ...System Register file KV4x Reference Manual Rev 2 02 2015 88 Preliminary Freescale Semiconductor Inc...
Страница 128: ...Debug Security KV4x Reference Manual Rev 2 02 2015 128 Preliminary Freescale Semiconductor Inc...
Страница 138: ...Boot KV4x Reference Manual Rev 2 02 2015 138 Preliminary Freescale Semiconductor Inc...
Страница 150: ...Pinout diagrams KV4x Reference Manual Rev 2 02 2015 150 Preliminary Freescale Semiconductor Inc...
Страница 170: ...Functional description KV4x Reference Manual Rev 2 02 2015 170 Preliminary Freescale Semiconductor Inc...
Страница 212: ...Functional description KV4x Reference Manual Rev 2 02 2015 212 Preliminary Freescale Semiconductor Inc...
Страница 284: ...Functional description KV4x Reference Manual Rev 2 02 2015 284 Preliminary Freescale Semiconductor Inc...
Страница 294: ...Functional description KV4x Reference Manual Rev 2 02 2015 294 Preliminary Freescale Semiconductor Inc...
Страница 330: ...Functional description KV4x Reference Manual Rev 2 02 2015 330 Preliminary Freescale Semiconductor Inc...
Страница 450: ...Initialization application information KV4x Reference Manual Rev 2 02 2015 450 Preliminary Freescale Semiconductor Inc...
Страница 512: ...Interrupts and DMA Requests KV4x Reference Manual Rev 2 02 2015 512 Preliminary Freescale Semiconductor Inc...
Страница 520: ...Memory Map and Register Descriptions KV4x Reference Manual Rev 2 02 2015 520 Preliminary Freescale Semiconductor Inc...
Страница 580: ...Initialization Application information KV4x Reference Manual Rev 2 02 2015 580 Preliminary Freescale Semiconductor Inc...
Страница 660: ...Functional description KV4x Reference Manual Rev 2 02 2015 660 Preliminary Freescale Semiconductor Inc...
Страница 1038: ...Example configuration for chained timers KV4x Reference Manual Rev 2 02 2015 1038 Preliminary Freescale Semiconductor Inc...
Страница 1074: ...Functional description KV4x Reference Manual Rev 2 02 2015 1074 Preliminary Freescale Semiconductor Inc...
Страница 1168: ...Initialization application information KV4x Reference Manual Rev 2 02 2015 1168 Preliminary Freescale Semiconductor Inc...
Страница 1264: ...Initialization application information KV4x Reference Manual Rev 2 02 2015 1264 Preliminary Freescale Semiconductor Inc...
Страница 1336: ...Functional description KV4x Reference Manual Rev 2 02 2015 1336 Preliminary Freescale Semiconductor Inc...
Страница 1358: ...KV4x Reference Manual Rev 2 02 2015 1358 Preliminary Freescale Semiconductor Inc...