UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1167 of 1269
NXP Semiconductors
UM10503
Chapter 45: LPC43xx DAC
If the DMA_ENA bit is set in the DAC CTRL register, the DAC DMA request will be routed
to the GPDMA. When the DMA_ENA bit is cleared, the default state after a reset, DAC
DMA requests are blocked.
45.6.2 Double buffering
Double-buffering is enabled only if both, the CNT_ENA and the DBLBUF_ENA bits are set
in DAC CTRL. In this case, any write to the DAC CR register will only load the pre-buffer,
which shares its register address with the DAC CR register. The DAC CR itself will be
loaded from the pre-buffer whenever the counter reaches zero and the DMA request is
set. At the same time the counter is reloaded with the CNTVAL register value.
Reading the DAC CR register will only return the contents of the DAC CR register itself,
not the contents of the pre-buffer register.
If either the CNT_ENA or the DBLBUF_ENA bits are 0, any writes to the DAC CR address
will go directly to the DAC CR register.
Fig 174. DAC control with DMA interrupt and timer
CNTVAL
COUNTER
PRE-BUFFER
MUX
CR
LD
LD
LD
EN
16
16
pbus
pbus
set_intrpt
dblbuf_ena
cnt_ena
ena_cnt_and_dblbuf
pbus_wr_to_CR
1
0
pbus
pbus
pbus_wr_to_CR
zero
DAC value
3
2
1
0
S
C
set_intrpt
pbus
pbus_wr_to_CR
DMA_ena
intrptDMA_req
CTRL