08M serial speeds


New Member
Is the 08M considered an 'X part' for the purpose of serial speeds? It does have the SERTXD at 4800 baud, like only an X part does. The documentation for SERIN and SEROUT suggest that the X parts have the 600/1200/2400/4800 baud speeds, and non-X parts have the 300/600/1200/2400 baud speeds instead. But it doesn't specifically say which speeds apply to an 'M part'.

What is the set of available speeds on the 08M? I've only used the 28X to date with the 4800 SERIN and SERTXD. I want to be able to use an 08M and a 28X together in a project, and thus have to work with a baud rate they both can do. I'd like to use SERTXD on the 28X to conserve output pin count, but that fixes the project at 4800 baud... which is no good if the 08M can't do 4800 SERIN.


Technical Support
Staff member
The 08M by default does SERIN and SEROUT at 300/600/1200/2400 with SERTXD at 4800, but by using 'SETFREQ M8' to switch to 8MHz operation it will do SERIN and SEROUT at 600/1200/2400/4800 with SERTXD at 9600.

Note the comments in the manuals about higher speed baud rates not being guaranteed on PICAXE's with internal oscillators, and the possible need to use 'CALIBFREQ' to fine tune the operating frequency.

I've personally had few problems with running higher speed baud rates between multiple PICAXE's and to PC's, but some equipment can be more finnicky. The 18X is perhaps the one with most potential problems having a wider manufacturer's tolerance ( not in Rev-Ed's control ) than the others, but I've had very few problems even with that.

Maximum SERIN/SEROUT baud rates are ...

08- 2400
08M 4800 (SETFREQ M8)
18- 2400
18A 4800 (SETFREQ M8)
18X 9600 (SETFREQ M8)
28- 4800 (8MHz XTAL)
28A 4800 (8MHz XTAL)
28X 19200 (16MHz XTAL)
40X 19200 (16MHz XTAL)

The 08M (SETFREQ M8) can do 9600 output only using SERTXD.

Edited by - hippy on 3/31/2005 2:54:44 PM