Marine VHF Audio and Signalling Processor
CMX885
7.10 Auxiliary DAC/RAMDAC Operation
The four Auxiliary DAC channels are programmed via the AuxDAC Control register, $A8. AuxDAC
channel 1 may also be programmed to operate as a RAMDAC which will automatically output a pre-
programmed profile at a programmed rate. The AuxDAC Control register, $A8, with b12 set, controls this
mode of operation. The default profile is a raised cosine (see Table 7), but this may be over-written with a
user defined profile by writing to Program Block P3.11. The RAMDAC operation is only available in Tx
mode and, to avoid glitches in the ramp profile, it is important not to change to Idle or Rx mode whilst the
RAMDAC is still ramping. The AuxDAC outputs (available on their respective DAC pins) hold the user-
programmed level during a powersave operation if left enabled, otherwise they will return to zero. Note
that access to all four AuxDACs is controlled by the AuxDAC Control register, $A8, and therefore to
update all AuxDACs requires four writes to this register. It is not possible to simultaneously update all four
AuxDACs.
See:
o
AuxDAC Control/Data – $A8 write
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D/885/3
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