
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
183 of 487
NXP Semiconductors
UM10800
Chapter 12: LPC82x DMA controller
If a channel is configured with the SWTRIG bit equal to 0, the channel can be later
triggered either by hardware or software. Software triggering is accomplished by writing a
1 to the appropriate bit in the SETTRIG register. Hardware triggering requires setup of the
HWTRIGEN, TRIGPOL, TRIGTYPE, and TRIGBURST fields in the CFG register for the
related channel. When a channel is initially set up, the SWTRIG bit in the XFERCFG
register can be set, causing the transfer to begin immediately.
Once triggered, transfer on a channel will be paced by DMA requests if the
PERIPHREQEN bit in the related CFG register is set. Otherwise, the transfer will proceed
at full speed.
The TRIG bit in the CTLSTAT register can be cleared at the end of a transfer, determined
by the value CLRTRIG (bit 0) in the XFERCFG register. When a 1 is found in CLRTRIG,
the trigger is cleared when the descriptor is exhausted.