UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
280 of 515
NXP Semiconductors
UM11029
Chapter 16: LPC84x DMA controller
16.6.18 Channel transfer configuration registers
The XFERCFGn register contains transfer related configuration information for DMA
channel n. Using the Reload bit, this register can optionally be automatically reloaded
when the current settings are exhausted (the full transfer count has been completed),
allowing linked transfers with more than one descriptor to be performed.
See
for details on trigger operation.
Table 320. Transfer Configuration registers for channel 0 to 24 (XFERCFG[0:24], addresses 0x5000 8408
(XFERCFG0) to 0x5000 856C (XFERCFG24)) bit description
Bit
Symbol
Value
Description
Reset
Value
0
CFGVALID
Configuration Valid flag. This bit indicates whether the current channel descriptor is
valid and can potentially be acted upon, if all other activation criteria are fulfilled.
0
0
Not valid. The channel descriptor is not considered valid until validated by an
associated SETVALID0 setting.
1
Valid. The current channel descriptor is considered valid.
1
RELOAD
Indicates whether the channel’s control structure will be reloaded when the current
descriptor is exhausted. Reloading allows ping-pong and linked transfers.
0
0
Disabled. Do not reload the channels’ control structure when the current descriptor
is exhausted.
1
Enabled. Reload the channels’ control structure when the current descriptor is
exhausted.
2
SWTRIG
Software Trigger.
0
0
When written by software, the trigger for this channel is not set. A new trigger, as
defined by the HWTRIGEN, TRIGPOL, and TRIGTYPE will be needed to start the
channel.
1
When written by software, the trigger for this channel is set immediately. This
feature should not be used with level triggering when TRIGBURST = 0.
3
CLRTRIG
Clear Trigger.
0
0
Not cleared. The trigger is not cleared when this descriptor is exhausted. If there is a
reload, the next descriptor will be started.
1
Cleared. The trigger is cleared when this descriptor is exhausted.
4
SETINTA
Set Interrupt flag A for this channel. There is no hardware distinction between
interrupt A and B. They can be used by software to assist with more complex
descriptor usage. By convention, interrupt A may be used when only one interrupt
flag is needed.
0
0
No effect.
1
Set. The INTA flag for this channel will be set when the current descriptor is
exhausted.
5
SETINTB
Set Interrupt flag B for this channel. There is no hardware distinction between
interrupt A and B. They can be used by software to assist with more complex
descriptor usage. By convention, interrupt A may be used when only one interrupt
flag is needed.
0
0
No effect.
1
Set. The INTB flag for this channel will be set when the current descriptor is
exhausted.
7:6
-
Reserved. Read value is undefined, only zero should be written.
NA