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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
525 of 808
NXP Semiconductors
UM10360
Chapter 26: LPC17xx Quadrature Encoder Interface (QEI)
6.3.11 QEI Velocity Capture register (QEICAP - 0x400B C034)
This register contains the most recently measured velocity of the encoder. This
corresponds to the number of velocity pulses counted in the previous velocity timer
period.The current velocity count is latched into this register when the velocity timer
overflows.
6.3.12 QEI Velocity Compare register (VELCOMP - 0x400B C038)
This register contains a velocity compare value. This value is compared against the
captured velocity in the velocity capture register. If the capture velocity is less than the
value in this compare register, a velocity compare interrupt (VELC_Int) will be asserted, if
enabled.
6.3.13 QEI Digital Filter register (FILTER - 0x400B C03C)
This register contains the sampling count for the digital filter. A sampling count of zero
bypasses the filter.
6.4 Interrupt registers
6.4.1 QEI Interrupt Status register (QEIINTSTAT)
This register provides the status of the encoder interface and the current set of interrupt
sources that are asserted to the controller. Bits set to 1 indicate the latched events that
have occurred; a zero bit indicates that the event in question has not occurred. Writing a 0
to a bit position clears the corresponding interrupt.
Table 479: QEI Velocity Capture register (QEICAP - address 0x400B C034) bit description
Bit
Symbol
Description
Reset
value
0:31
-
Current velocity pulse count.
0
Table 480: QEI Velocity Compare register (VELCOMP - address 0x400B C038) bit description
Bit
Symbol
Description
Reset
value
0:31
-
Current velocity pulse count.
0
Table 481: QEI Digital Filter register (FILTER - address 0x400B C03C) bit description
Bit
Symbol
Description
Reset
value
0:31
-
Digital filter sampling delay
0x0