UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 500 of 841
NXP Semiconductors
UM10360
Chapter 21: LPC176x/5x Timer 0/1/2/3
the GPDMA controller.
Remark: Because timer DMA requests are generated whenever the timer value is equal
to the related Match Register value, DMA requests are always generated when the timer
is running, unless the Match Register value is higher than the upper count limit of the
timer. It is important not to select and enable timer DMA requests in the GPDMA block
unless the timer is correctly configured to generate valid DMA requests.
21.7 Example timer operation
Figure 114 shows a timer configured to reset the count and generate an interrupt on
match. The prescaler is set to 2 and the match register set to 6. At the end of the timer
cycle where the match occurs, the timer count is reset. This gives a full length cycle to the
match value. The interrupt indicating that a match occurred is generated in the next clock
after the timer reached the match value.
Figure 115
shows a timer configured to stop and generate an interrupt on match. The
prescaler is again set to 2 and the match register set to 6. In the next clock after the timer
reaches the match value, the timer enable bit in TCR is cleared, and the interrupt
indicating that a match occurred is generated.
Fig 114. A timer cycle in which PR=2, MRx=6, and both interrupt and reset on match are enabled.
PCLK
prescale
counter
interrupt
timer
counter
timer counter
reset
222200001111
45 6 0 1
Fig 115. A timer Cycle in Which PR=2, MRx=6, and both interrupt and stop on match are enabled
PCLK
prescale counter
interrupt
timer counter
TCR[0]
(counter enable)
220 01
45 6
1 0
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