LM3S8971 Datasheet, PDF (508/577 Pages) List of Unclassifed Manufacturers – Microcontroller

Quadrature Encoder Interface (QEI)
Register 1: QEI Control (QEICTL), offset 0x000
This register contains the configuration of the QEI module. Separate enables are provided for the
quadrature encoder and the velocity capture blocks; the quadrature encoder must be enabled in
order to capture the velocity, but the velocity does not need to be captured in applications that do
not need it. The phase signal interpretation, phase swap, Position Update mode, Position Reset
mode, and velocity predivider are all set via this register.
QEI Control (QEICTL)
QEI0 base: 0x4002.C000
Offset 0x000
Type R/W, reset 0x0000.0000
31
30
29
28
27
Type RO
RO
RO
RO
RO
Reset
0
0
0
0
0
15
14
13
12
11
reserved
STALLEN INVI
Type RO
RO
RO
R/W
R/W
Reset
0
0
0
0
0
26
RO
0
10
INVB
R/W
0
25
RO
0
9
INVA
R/W
0
24
23
22
reserved
RO
RO
RO
0
0
0
8
7
6
VelDiv
R/W
R/W
R/W
0
0
0
21
20
19
18
17
16
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
5
4
3
2
1
VelEn ResMode CapMode SigMode Swap
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
Enable
R/W
0
Bit/Field
31:13
12
11
10
9
8:6
Name
reserved
STALLEN
INVI
INVB
INVA
VelDiv
Type
RO
R/W
R/W
R/W
R/W
R/W
Reset
0x00
0
0
0
0
0x0
Description
Software should not rely on the value of a reserved bit. To provide
compatibility with future products, the value of a reserved bit should be
preserved across a read-modify-write operation.
Stall QEI
When set, the QEI stalls when the microcontroller asserts Halt.
Invert Index Pulse
When set , the input Index Pulse is inverted.
Invert PhB
When set, the PhB input is inverted.
Invert PhA
When set, the PhA input is inverted.
Predivide Velocity
A predivider of the input quadrature pulses before being applied to the
QEICOUNT accumulator. This field can be set to the following values:
Value Predivider
0x0
÷1
0x1
÷2
0x2
÷4
0x3
÷8
0x4 ÷16
0x5 ÷32
0x6 ÷64
0x7 ÷128
508
October 01, 2007
Preliminary