UM10850
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User manual
Rev. 2.4 — 13 September 2016
220 of 464
NXP Semiconductors
UM10850
Chapter 14: LPC5410x Standard counter/timers (CT32B0/1/2/3/4)
14.8.2 DMA operation
DMA requests are generated by a match of the Timer Counter (TC) register value to either
Match Register 0 (MR0) or Match Register 1 (MR1). This is not connected to the operation
of the Match outputs controlled by the EMR register. Each match sets a DMA request flag,
which is connected to the DMA controller. In order to have an effect, the DMA controller
must be configured correctly.
When a timer is initially set up to generate a DMA request, the request may already be
asserted before a match condition occurs. An initial DMA request may be avoided by
having software write a one to the interrupt flag location, as if clearing a timer interrupt.
See
. A DMA request will be cleared automatically when it is acted upon by
the DMA controller.
Note:
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 DMA block unless the
timer is correctly configured to generate valid DMA requests.