ROM-Resident Routine PUTBYTE

[Brusse]

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.

[bigmac]

Hello Brusse,

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

Regards,
Mac

[Brusse]

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?)

[bigmac]

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

[gbm]

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