topic ROM-Resident Routine PUTBYTE in 8-bit Microcontrollers

ROM-Resident Routine PUTBYTE

Brusse — Mon, 03 Apr 2006 18:41:21 GMT

Hi,

Is it possible to use then ROM-Resident Routine PUTBYTE in a 68HC908QT4 (Classic). I found the routine in the new improved 68HC908QT4A but can´t find any documentation about Classic.

Re: ROM-Resident Routine PUTBYTE

gbm — Tue, 04 Apr 2006 21:24:49 GMT

Yes, it is possible. The built in monitor code uses it.

Re: ROM-Resident Routine PUTBYTE

bigmac — Tue, 04 Apr 2006 22:12:36 GMT

Hello Brusse,

The PUTBYTE routine should be located at address $FED0 for the QT4 (classic).

Regards,
Mac

Re: ROM-Resident Routine PUTBYTE

Brusse — Tue, 04 Apr 2006 22:25:57 GMT

Many thanks, Mac

Do you know if there is any special conciderations to deal with before i make a call to the routine, i guess the charater to be send should be held in Acc. (have you found this information in some docs?)

Re: ROM-Resident Routine PUTBYTE

bigmac — Wed, 05 Apr 2006 13:39:25 GMT

Hello Bru,

Have a look at AN1831 (Rev 3), where the code for the ROM routine RDVRRNG makes a call to PUTBYTE. I think I have also read that the H:X register value is preserved by PUTBYTE.

I have not yet done so myself, but it may not be too onorous to disassemble this code, using an actual device, to find out how the routine works.

Regards,
Mac