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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
558 of 808
NXP Semiconductors
UM10360
Chapter 30: LPC17xx Digital-to-Analog Converter (DAC)
4.
Register description
The DAC registers are shown in
. Note that the DAC does not have a control
bit in the PCONP register. To enable the DAC, its output must be selected to appear on
the related pin, P0.26, by configuring the PINSEL1 register. See
Function Select Register 1 (PINSEL1 - 0x4002 C004)”
. the DAC must be enabled in this
manner prior to accessing any DAC registers.
[1]
Reset value reflects the data stored in used bits only. It does not include reserved bits content.
4.1 D/A Converter Register (DACR - 0x4008 C000)
This read/write register includes the digital value to be converted to analog, and a bit that
trades off performance vs. power. Bits 5:0 are reserved for future, higher-resolution D/A
converters.
[1]
The settling times noted in the description of the BIAS bit are valid for a capacitance load on the AOUT pin
not exceeding 100 pF. A load impedance value greater than that value will cause settling time longer than
the specified time. One or more graph(s) of load impedance vs. settling time will be included in the final data
sheet.
4.2 D/A Converter Control register (DACCTRL - 0x4008 C004)
This read/write register enables the DMA operation and controls the DMA timer.
Table 520. DAC registers
Name
Description
Access
Reset value
Address
DACR
D/A Converter Register. This register contains the digital
value to be converted to analog and a power control bit.
R/W
0
0x4008 C000
DACCTRL
DAC Control register. This register controls DMA and timer
operation.
R/W
0
0x4008 C004
DACCNTVAL
DAC Counter Value register. This register contains the
reload value for the DAC DMA/Interrupt timer.
R/W
0x0000 0000
0x4008 C008
Table 521: D/A Converter Register (DACR - address 0x4008 C000) bit description
Bit
Symbol Value
Description
Reset
Value
5:0
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
15:6
VALUE
After the selected settling time after this field is written with a
new VALUE, the voltage on the AOUT pin (with respect to
V
SSA
) is VALUE/1024
×
VREF.
0
16
0
The settling time of the DAC is 1
μ
s max, and the maximum
current is 700
μ
A.
0
1
The settling time of the DAC is 2.5
μ
s and the maximum
current is 350
μ
A.
31:17 -
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA