© 2004 Microchip Technology Inc. DS70063C-page 16-5
Section 16. Quadrature Encoder Interface (QEI)
Quadrature Encoder
Interface (QEI)
16
Register 16-1: QEICON: QEI Control Register
Upper Byte:
R/W-0 U-0 R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0
CNTERR — QEISIDL INDEX UPDN QEIM<2:0>
bit 15 bit 8
Lower Byte:
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
SWPAB PCDOUT TQGATE TQCKPS<1:0> POSRES TQCS UDSRC
bit 7 bit 0
bit 15 CNTERR: Count Error Status Flag bit
1 = Position count error has occurred
0 = No position count error has occurred
(CNTERR flag only applies when QEIM<2:0> = ‘110’ or ‘100’)
bit 14 Unimplemented: Read as ‘0’
bit 13 QEISIDL: Stop in Idle Mode bit
1 = Discontinue module operation when device enters Idle mode
0 = Continue module operation in Idle mode
bit 12 INDEX: Index Pin State Status bit (Read Only)
1 = Index pin is High
0 = Index pin is Low
bit 11 UPDN: Position Counter Direction Status bit
1 = Position Counter Direction is positive (+)
0 = Position Counter Direction is negative (-)
(Read only bit when QEIM<2:0> = ‘1XX’)
(Read/Write bit when QEIM<2:0> = ‘001’)
bit 10-8 QEIM<2:0>: Quadrature Encoder Interface Mode Select bits
111 = Quadrature Encoder Interface enabled (x4 mode) with position counter reset by match (MAXCNT)
110 = Quadrature Encoder Interface enabled (x4 mode) with Index Pulse reset of position counter
101 = Quadrature Encoder Interface enabled (x2 mode) with position counter reset by match (MAXCNT)
100 = Quadrature Encoder Interface enabled (x2 mode) with Index Pulse reset of position counter
011 = Unused (Module disabled)
010 = Unused (Module disabled)
001 = Starts 16-bit Timer
000 = Quadrature Encoder Interface/Timer off
bit 7 SWPAB: Phase A and Phase B Input Swap Select bit
1 = Phase A and Phase B inputs swapped
0 = Phase A and Phase B inputs not swapped
bit 6 PCDOUT: Position Counter Direction State Output Enable bit
1 = Position Counter Direction Status Output Enable (QEI logic controls state of I/O pin)
0 = Position Counter Direction Status Output Disabled (Normal I/O pin operation)
bit 5 TQGATE: Timer Gated Time Accumulation Enable bit
1 = Timer gated time accumulation enabled
0 = Timer gated time accumulation disabled
bit 4-3 TQCKPS<1:0>: Timer Input Clock Prescale Select bits
11 = 1:256 prescale value
10 = 1:64 prescale value
01 = 1:8 prescale value
00 = 1:1 prescale value
(Prescaler utilized for 16-bit timer mode only)
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