F8D
F8E
0
F8F
...
2
1
24 23
21
22
F9D
F9E
F9F
20
F9B
F9C
F9A
F97
F98
F99
QA
QB
QCLK
QEPSTS:QDF
QPOSCNT F8C
24
25
F8F
0
QI
Index interrupt/
index event
marker
QPOSILAT
QEPSTS:QDLF
Position Counter and Control Unit (PCCU)
830
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Enhanced QEP (eQEP) Module
For example, if the first reset operation occurs on the falling edge of QEPB during the forward direction,
then all the subsequent reset must be aligned with the falling edge of QEPB for the forward rotation and
on the rising edge of QEPB for the reverse rotation as shown in
.
The position-counter value is latched to the QPOSILAT register and direction information is recorded in
the QEPSTS[QDLF] bit on every index event marker. The position-counter error flag (QEPSTS[PCEF])
and error interrupt flag (QFLG[PCE]) are set if the latched value is not equal to 0 or QPOSMAX. The
position-counter error flag (QEPSTS[PCEF]) is updated on every index event marker and an interrupt flag
(QFLG[PCE]) will be set on error that can be cleared only through software.
The index event latch configuration QEPCTL[IEL] bits are ignored in this mode and position counter error
flag/interrupt flag are generated only in index event reset mode.
Figure 9-8. Position Counter Reset by Index Pulse for 1000 Line Encoder (QPOSMAX = 3999 or 0xF9F)
9.4.1.2
Position Counter Reset on Maximum Position (QEPCTL[PCRM]=01)
If the position counter is equal to QPOSMAX, then the position counter is reset to 0 on the next eQEP
clock for forward movement and position counter overflow flag is set. If the position counter is equal to
ZERO, then the position counter is reset to QPOSMAX on the next QEP clock for reverse movement and
position counter underflow flag is set.
shows the position counter reset operation in this mode.
The first index marker fields (QEPSTS[FIDF] and QEPSTS[FIMF]) are not applicable in this mode.