MC9S12DG256B vs. MC9S12DG256 differences (i.e. Port T)

[darrin]

We were using an 9S12DG256Bcpv and had no problems.

Now we have to buy the 9S12DG256cpv (since the B part is obsolete) and find the PORT T bit0 &1 do not output.

DDRT = 255;

for (; ; )

{

PTT = 0;

asm nop;

PTT = 255;

asm nop;

}

if you read PTIT reg it shows 3 when PTT = 0

I dont use any of the timer/capture registers.

please help.

[Nabla69]

Hello Darrin,

The Datasheet of the DG256 I have = 9S12DT256DGV3/D states Port T bits 0 to 7 are Inputs and Outputs.

In you configuration PTIT is supposed to read the same as PTT.

Your part can be damaged. What kind of load do you have on PTT0 and PTT1 ?

Alvin.

[darrin]

I use this part in different designs. One particular design I have does not use Port T at all. (pins are open).

And yet it exhibits the same symptoms (bit 0 & 1 appear to stay as inputs).

I even removed the DG256cpv and replaced it with a DG256Bcpv and ran the same code. And bit 0 & 1 toggle like they are supposed too.

[darrin]

I also found (using the BDM debugger) that the INITIAL state of the chip shows

PTT = 3 and PTIT = 3 and DDRT  = 0 (even though all the PORT T pins are open)

I even lifted the pins just to make sure there is no PCB problem.

All the timer registers show 0 (as they should), so PORT T is not set up as a timer / capture pin.