• DOWN-count mode
7.4.1.1 Quadrature Count Mode
The quadrature decoder generates the direction and clock to the position counter in quadrature count mode.
Direction
Decoding
The direction decoding logic of the eQEP circuit determines which one of the sequences
(QEPA, QEPB) is the leading sequence and accordingly updates the direction information in the
QEPSTS[QDF] bit.
show the direction decoding logic in truth table and
state machine form. Both edges of the QEPA and QEPB signals are sensed to generate count
pulses for the position counter. Therefore, the frequency of the clock generated by the eQEP logic
is four times that of each input sequence.
shows the direction decoding and clock
generation from the eQEP input signals.
Table 7-2. Quadrature Decoder Truth Table
Previous Edge
Present Edge
QDIR
QPOSCNT
QA↑
QB↑
UP
Increment
QB↓
DOWN
Decrement
QA↓
TOGGLE
Increment or Decrement
QA↓
QB↓
UP
Increment
QB↑
DOWN
Decrement
QA↑
TOGGLE
Increment or Decrement
QB↑
QA↑
DOWN
Decrement
QA↓
UP
Increment
QB↓
TOGGLE
Increment or Decrement
QB↓
QA↓
DOWN
Decrement
QA↑
UP
Increment
QB↑
TOGGLE
Increment or Decrement
(00)
(10)
(11)
(01)
(A,B)=
QEPA
QEPB
eQEP signals
10
01
00
11
Increment
counter
Decrement
counter
Decrement
counter
Increment
counter
Decrement
counter
Decrement
counter
Increment
counter
Increment
counter
Figure 7-6. Quadrature Decoder State Machine
Enhanced Quadrature Encoder Pulse (eQEP)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
469
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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