Steve,

Thankyou for replying to one of my posts again.

I have never tried connecting a PIC to a PC though I'm looking into it.

The other option you suggested with the DEFINE didn't work.

Perhaps it may be a bug with the old 2.04 version I have. I looked at the modedefs.bas file and it does contain both N and T300.

I've been hammering away at this for over a week now to no avail.

One thing I found which I was mistaken about was that my PBP version goes only to 16F84 and not the 16F84A PICs I'm using.
Strange that I seem to be able to compile and run the programs most of the time without a problem. This could well be the root of the N&T300 problem I suppose.

What do you think of using T1200 with CHAR_PACING 3000 to slow it down to (I think) approx 33 BPS? I need a slow BPS as I'm trying to transmit a single byte of serial data ultrasonically, 24kHz to start with then perhaps 40kHz. At the moment I have SEROUT from the TX 16F84A going to a 555 timer at 24kHz then on to a 4069 buffer for maximium 9V V+ to the transducer. It's not working or should I say I only got it going once or twice and then only short range and sporadically. T1200 was too fast hence the need for T300 and the 555 wasn't passing on the PICs SEROUT very well either. Connected directly via a wire TX PIC to RX PIC was good but TX PIC to 555 to RX PIC was poor. A very low byte "match" rate. I think it's the 555 55% duty cycle.

I read that a TMR interrupt can be used to toggle an output pin at 24/40kHz connected to the input of an AND gate while another output pin is connected to the remaining AND gate input to toggle the carrier on and off to send data. The AND gates can be used to switch transistors for a higher than 5V supply to the transducer. This sounds good but is beyond me and I thought that PICs where incapable of multitaking? Isn't this multitasking?

Regards,

Andrew.