Datasheet

REV. B
ADuC824
–41–
USER INTERFACE TO OTHER ON-CHIP ADuC824
PERIPHERALS
The following section gives a brief overview of the various peripher-
als also available on-chip. A summary of the SFRs used to control
and configure these peripherals is also given.
DAC
The ADuC824 incorporates a 12-bit, voltage output DAC on-chip.
It has a rail-to-rail voltage output buffer capable of driving
10 kΩ/100 pF. It has two selectable ranges, 0 V to V
REF
(the inter-
nal bandgap 2.5 V reference) and 0 V to AV
DD
. It can operate in
12-bit or 8-bit mode. The DAC has a control register, DACCON,
and two data registers, DACH/L. The DAC output can be
programmed to appear at Pin 3 or Pin 12. It should be noted
that in 12-bit mode, the DAC voltage output will be updated as
soon as the DACL data SFR has been written; therefore, the DAC
data register should be updated as DACH first followed by DACL.
DACH/L DAC Data Register
Function DAC Data Registers, written by user to update the DAC output.
SFR Address DACL (DAC Data Low Byte) –>FBH
DACH (DAC Data High Byte) –>FCH
Power-On Default Value 00H –>Both Registers
Bit Addressable No –>Both Registers
The 12-bit DAC data should be written into DACH/L right-justified such that DACL contains the lower eight bits, and the lower
nibble of DACH contains the upper four bits.
DACCON DAC Control Register
SFR Address FDH
Power-On Default Value 00H
Bit Addressable No
Table XVI. DACCON SFR Bit Designations
Bit Name Description
7 — Reserved for Future Use
6 — Reserved for Future Use
5 — Reserved for Future Use
4 DACPIN DAC Output Pin Select
Set by user to direct the DAC output to Pin 12 (P1.7/AIN4/DAC).
Cleared by user to direct the DAC output to Pin 3 (P1.2/DAC/IEXC1).
3 DAC8 DAC 8-Bit Mode Bit
Set by user to enable 8-bit DAC operation. In this mode the 8-bits in DACL SFR are routed to the
8 MSBs of the DAC and the 4 LSBs of the DAC are set to zero.
Cleared by user to operate the DAC in its normal 12-bit mode of operation.
2 DACRN DAC Output Range Bit
Set by user to configure DAC range of 0 –AV
DD
.
Cleared by user to configure DAC range 0 – 2.5 V.
1 DACCLR DAC Clear Bit
Set to ‘1’ by user to enable normal DAC operation.
Cleared to ‘0’ by used to reset DAC data registers DAC1/H to zero.
0 DACEN DAC Enable Bit
Set to ‘1’ by user to enable normal DAC operation.
Cleared to ‘0’ by used to power-down the DAC.
———DACPIN DAC8 DACRN DACCLR DACEN