51MM256: What/where is "DAC5BIT" ?

[WadeH]

An entity called "DAC5BIT" is named as one of the input-sources to the two onboard op-amps on the 51MM256.

I can find no other reference in the RM to 'DAC5BIT'.

Can anyone tell me what this is? (It looks very useful.)

Wade Hassler

[TomE]

If you type "DAC5BIT" into the search page on www.freescale.com you'll find matches in both the MC51MM and MC9S08MM manuals. Ditto for "DAC12BIT". I'm a bit surprised these keywords (and other ones I've tried that are in the OPAMP chapter) only show up for those two series of chips. So there doesn't seem to be any "prior history" for this module.

I initially agreed with Jim, except it looked like Freescale might have designed (or bought in) this Module with the expectation of the chips it was built into having two DACs, and then never used it that way. BUT...

If you look at this manual:

http://cache.freescale.com/files/32bit/doc/ref_manual/K53P144M100SF2V2RM.pdf?fsrch=1&sr=2

it details the module connections for that particular chip, and in it the OPAMP connects to "12-bit DAC0 output" and "CMP0 6-bit DAC output".

The PRACMP in the chip you're using has a 5-bit DAC connected to "PRG output" so I think there's a good chance that goes to the DAC5BIT input on the OPAMPs. Test it and let us know.

The Block Diagrams show the DAC output going to the DAC0 pin and to the OPAMPs. It also shows it going to what looks to be the VINPx pins of the two TRIAMPs. The TRIAMP documentation mentions having VINP connected to a pad, and in the tables shows having Vdac set to zero and 0.2V. There's nothing in the manual stating how to select between driving VINPx from the pin or the DAC though. This might cause problems for anyone trying to use this module.

Tom

[JimDon]

My guess would be that this die has no DAC5BIT, but the mux input is reserved for it.