Texas Instruments MSP430x4xx - Manual (Page 455)

DAC12 Operation
23-9 DAC12
23.2.6 Grouping Multiple DAC12 Modules
Multiple DAC12s can be grouped together with the DAC12GRP bit to
synchronize the update of each DAC12 output. Hardware ensures that all
DAC12 modules in a group update simultaneously independent of any
interrupt or NMI event.
On the MSP430FG43x devices, DAC12_0 and DAC12_1 are grouped by
setting the DAC12GRP bit of DAC12_0. The DAC12GRP bit of DAC12_1 is
don’t care. When DAC12_0 and DAC12_1 are grouped:
- The DAC12_1 DAC12LSELx bits select the update trigger for both DACs
- The DAC12LSELx bits for both DACs must be > 0
- The DAC12ENC bits of both DACs must be set to 1
When DAC12_0 and DAC12_1 are grouped, both DAC12_xDAT registers
must be written to before the outputs update - even if data for one or both of
the DACs is not changed. Figure 23−7 shows a latch-update timing example
for grouped DAC12_0 and DAC12_1.
When DAC12_0 DAC12GRP = 1 and both DAC12_x DAC12LSELx > 0 and
either DAC12ENC = 0, neither DAC12 will update.
Figure 23−7. DAC12 Group Update Example, Timer_A3 Trigger
DAC12_0
DAC12GRP
DAC12_0
DAC12ENC
TimerA_OUT1
DAC12_0
Latch Trigger
DAC12_0 Updated
DAC12_0 DAC12LSELx = 2 DAC12_0 DAC12LSELx > 0 AND
DAC12_1 DAC12LSELx = 2
DAC12_0DAT
New Data
DAC12_1DAT
New Data
DAC12_0 and DAC12_1
Updated Simultaneously
Note: DAC12 Settling Time
The DMA controller is capable of transferring data to the DAC12 faster than
the DAC12 output can settle. The user must assure the DAC12 settling time
is not violated when using the DMA controller. See the device-specific data
sheet for parameters.