DAC Operating Modes
6.3
The DAC part of the TPMC851 can operate in two modes – Immediate Update or Simultaneous Update. These
modes are configured with the Load Mode Select (LOADSEL) bits in the DAC Control Register DACCONT.
LOADSEL[1:0]
Load Mode
Immediate Update
00
Immediate Update:
The DAC outputs are updated immediately on a
write access to a DAC Data Register
Simultaneous Update
01
Simultaneous Update:
All DAC outputs are updated simultaneously when
LOADDAC is set to ‘1’
10
Sequencer Update:
All DAC outputs are updated simultaneously when
the DAC Sequencer Timer reaches zero
11
Trigger Update:
All DAC outputs are updated simultaneously by an
external trigger (Dig I/O Line 1)
Table 6-2 : DAC Load Modes
6.3.1 Immediate Update
The DACs are updated immediately on a write access to a DAC Data Register. Use this mode if single channels
need to be updated on an irregular base.
6.3.2 Simultaneous Update
Write accesses to the DAC Data Registers don’t immediately update the DACs. Instead this data is buffered until
a trigger event. This trigger event simultaneously updates all DACs with the buffered data. The Simultaneous
Update Mode divides into three sub modes. These modes vary in the source for the trigger event:
x
Simultaneous Update: The DACs are updated simultaneously when LOADDAC in the DAC Control
Register DACCONT is set to ‘1’. Use this mode if all channels need to be updated on an irregular base.
x
Sequencer Update: All DAC outputs are updated simultaneously when the DAC Sequencer Timer
reaches zero. Use this mode if all channels need to be updated on a regular base.
x
Trigger Update: All DAC outputs are updated simultaneously by an external trigger (Dig I/O Line 1). Use
this mode if all channels need to be updated on an external event.
Before a simultaneous update all DACs should be loaded with new data via the DAC Data Registers. If a channel
was not loaded with new data, it will use the old data previously buffered.
Allow the DAC outputs to settle for approx. 10μs before performing a new DAC update.
TPMC851 User Manual Issue 1.0.9
Page 55 of 65
