topic Re: QG8 PTB0 looks like PTA4 in 8-bit Microcontrollers

QG8 PTB0 looks like PTA4

blinari — Thu, 19 Jul 2007 02:27:55 GMT

I am running the DEMO9S08QG8 board I set all my inputs and output the way that I want them using the Processor Expert as a KBI. I set PTB0 to an input (KBI) that is driven by 100 ohm output resistant source and PTB0 looks like PTA4 (the debug data) with a some of the real signal? If I get rid of the input it look almost the same as PTA4. It looks high impedance between PTA4 and PTB0 like 2Mohm and all the corners are rounded.

How do I get PTB0 to not follow PTA4 so I can use PTB0.

Re: QG8 PTB0 looks like PTA4

peg — Sat, 21 Jul 2007 08:16:19 GMT

Hi blinari,

I am not sure if I follow you (pun intended) but here goes:

PTA4 shares with BKGD on a QG8 so you have to be careful about using both uses of this pin.

On a DEMOQG8 board this pin is hard-wired into the BDM converter section, so using it for anything else is nigh on impossible with board modifications.

PTB0 shares with RXD. This pin on the DEMOQG8 board is hardwired to the MAX3218 so the same sort of things apply here.

PTA0, PTA1, PTA2, PTA3, PTB2, PTB3, PTB4, PTB5, PTB6 and PTB7 are really the only ones freely available for other uses on this demo board. (If you remove the USER EN jumpers.

PTB0, PTB1 are used for comms and PTA4, PTA5 are used for BDM.

Hope this helps.

Re: QG8 PTB0 looks like PTA4

peg — Sun, 22 Jul 2007 06:10:30 GMT

Hello blinari,

I read your question again today and I think I mis-interpreted it yesterday.

I now believe you are saying that PTB0 is tracking the BDM comms on PTA4/BKGD.

What I said before I still believe is correct but perhaps not so relevant to your problem.

I now think the answer is to remove the jumper between 2 and 3 of COM_EN.

If you want to disable the MAX3218 to free-up PTB0 but still use BKGD you need to place the jumper on COM_EN between 1 and 2.

COM_EN 2 to 3 connects BKGD to FORCEON/OFF of the MAX3218. So the signal you are seeing on PTB0 is probably the reciever coming in and out of tri-state mode.

Re: QG8 PTB0 looks like PTA4

blinari — Tue, 24 Jul 2007 01:34:32 GMT

What you said was true and I needed to do that, but I could not configure PTB0 as an output. I was able to toggle all of the other pins (exept the for the Debug pins and not PTB0). But then I looked at the Bean output "void PE_low_level_init(void)", and it was not setting PTBDD bit 0 as an output. I changed that and it works!

Thanks for your help