Philip, Tom,

I don't use either basic so i am not speaking from experience. If Tiny Basic uses Timer 1 i would expect it to run on the '420. As i recall Tiny Basic is integer Basic.

Review of intel's source for BASIC-52 (all i have although i know there are other "mod'd" versions) clearly shows the use of instruction cycle timing to determine bit rate so i am surprised that you got it running on reduced machine cycle per instruction devices. What am i missing? Did you use the intel source or another version?

Philip, since you are modifying the source why not input your bit rate into timer two delay just a bit and then just "jam load" a character into SBUF and look to see if it outputs at the correct bit rate. I haven't looked at the source exhaustively but even if interrupts are off the "jam load" into SBUF will cause output to your terminal device.

regards,
p