UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
276 of 515
NXP Semiconductors
UM11029
Chapter 16: LPC84x DMA controller
The CFGVALID and SV (set valid) bits allow more direct DMA block timing control by
software. Each Channel Descriptor, in a sequence of descriptors, can be validated by
either the setting of the CFGVALID bit or by setting the channel's SETVALID flag.
Normally, the CFGVALID bit is set. This tells the DMA that the Channel Descriptor is
active and can be executed. The DMA will continue sequencing through descriptor blocks
whose CFGVALID bit are set without further software intervention. Leaving a CFGVALID
bit set to 0 allows the DMA sequence to pause at the Descriptor until software triggers the
continuation. If, during DMA transmission, a Channel Descriptor is found with CFGVALID
set to 0, the DMA checks for a previously buffered SETVALID0 setting for the channel. If
found, the DMA will set the descriptor valid, clear the SV setting, and resume processing
the descriptor. Otherwise, the DMA pauses until the channels SETVALID0 bit is set.
16.6.14 Set Trigger register
The SETTRIG0 register allows setting the TRIG bit in the CTRLSTAT register for one or
more DMA channel. See
for a description of the TRIG bit, and
for a general description of triggering.
16.6.15 Abort registers
The Abort0 register allows aborting operation of a DMA channel if needed. To abort a
selected channel, the channel should first be disabled by clearing the corresponding
Enable bit by writing a 1 to the proper bit ENABLECLR. Then wait until the channel is no
longer busy by checking the corresponding bit in BUSY. Finally, write a 1 to the proper bit
of ABORT. This prevents the channel from restarting an incomplete operation when it is
enabled again.
Table 314. Set Valid 0 register (SETVALID0, address 0x5000 8068) bit description
Bit
Symbol
Description
Reset value
24:0
SV
SETVALID control for DMA channel n. Bit n corresponds to
DMA channel n.
0 = no effect.
1 = sets the VALIDPENDING control bit for DMA channel n.
NA
31:25 -
Reserved.
-
Table 315. Set Trigger 0 register (SETTRIG0, address 0x5000 8070) bit description
Bit
Symbol
Description
Reset value
24:0
TRIG
Set Trigger control bit for DMA channel 0. Bit n corresponds to
DMA channel n.
0 = no effect.
1 = sets the TRIG bit for DMA channel n.
NA
31:25 -
Reserved.
-
Table 316. Abort 0 register (ABORT0, address 0x5000 8078) bit description
Bit
Symbol
Description
Reset
value
24:0
ABORTCTRL Abort control for DMA channel 0. Bit n corresponds to DMA
channel n.
0 = no effect.
1 = aborts DMA operations on channel n.
NA
31:25 -
Reserved.
-