UM10503
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User manual
Rev. 1.3 — 6 July 2012
1166 of 1269
NXP Semiconductors
UM10503
Chapter 45: LPC43xx DAC
45.5.3 D/A Converter Counter Value register
This read/write register contains the reload value for the Interrupt/DMA counter.
45.6 Functional description
45.6.1 DMA counter
When the counter enable bit CNT_ENA in DAC CTRL register is set, a 16-bit counter will
begin counting down, at the rate selected by CLK_APB3_DAC, from the value
programmed into the DAC CNTVAL register. The counter is decremented each time the
counter reaches zero, the counter will be reloaded by the value of the DAC CNTVAL
register and the DMA request bit INT_DMA_REQ will be set in hardware.
Note that the contents of the DAC CTRL and DAC CNTVAL registers are read and write
accessible, but the timer itself is not accessible for either read or write.
Table 1019.D/A Control register (CTRL - address 0x400E 1004) bit description
Bit
Symbol
Value Description
Reset
value
0
INT_DMA_REQ
DMA request
0
0
This bit is cleared on any write to the DAC CR register.
1
This bit is set by hardware when the timer times out.
1
DBLBUF_ENA
DMA double-buffering
0
0
Disable double-buffering.
1
Enable double-buffering. When this bit and the
CNT_ENA bit are both set, the double-buffering feature
in the DAC CR register will be enabled. Writes to the
DAC CR register are written to a pre-buffer and then
transferred to the DAC CR on the next time-out of the
counter.
2
CNT_ENA
DMA time-out
0
0
Time-out counter operation is disabled.
1
Time-out counter operation is enabled.
3
DMA_ENA
DAC and DMA enable
0
0
Disable DMA/DMA.
1
Enable DAC and DMA Burst Request Input 15 (see
31:4
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
-
Table 1020:D/A Converter counter value register (CNTVAL - address 0x400E 1008) bit
description
Bit
Symbol
Description
Reset value
15:0
VALUE
16-bit reload value for the DAC interrupt/DMA timer.
0
31:16 -
Reserved.
-