S08 QD2 wont run code if PTA4 has 10K Ohm load

[CarlFST60L_3rd]

Hi guys,

Any idea's why my code wont run when I run a 10K Ohm to ground on PTA4?

The software just sets SOPT1 to 0x00 so there is no BDM. The code just toggles PTA4 at 500uS. No load, it works great, add 30K Ohm to ground, still works great, change to 10K Ohm, the output just sits at about Vcc/2 (3.3V / 2). Not, I am only talking about powering it up. If I power up with no load on PTA4, then connect the load, its works fine.

I have also even tried setting up PTADS_PTADS4 = 1; PTADD_PTADD4 = 1;

It appears that the processor just cannot boot with any load less thant about 15K ohm.

Carl.

[kef]

That's expected behaviour, I think. Pulling BGND/MS pin low at power on should make part entering active BDM mode. For normal operation part should boot with BGND/MS pulled high.

[CarlFST60L_3rd]

I cannot see this in the data sheet. And it poweres up fine with a 30K Ohm to ground, even 27K Ohm to ground. But when I power it up with 10K Ohm to gound, the processor will not even run 1 line of code, it just sits there forever doing 'nothing'. This is normal??

[kef]

QD4 Datasheet rev3.

Figure 2-2. Basic System Connections. Note1 "... BDM can be entered by holding MS low during POR ... "

2.2.4 Background / Mode Select (BKGD/MS)

During a power-on-reset (POR) or background debug force reset (see Section 5.8.3, “System Background Debug Force Reset Register (SBDFR)” for more information), the PTA4/TPM2CH0O/BKGD/MS pin functions as a mode select pin....

...

If nothing is connected to this pin (kef: note that MS pin pull-up is active after reset), the MCU will enter normal operating mode at the rising edge of the internal reset after a POR or force BDC reset. If a debug system is connected to the 6-pin standard background debug header, it can hold BKGD/MS low during a POR or immediately after issuing a background debug force reset, which will force the MCU to active background mode.

3.4 Active Background Mode

The active background mode functions are managed through the background debug controller (BDC) in the HCS08 core. The BDC provides the means for analyzing MCU operation during software development.

Active background mode is entered in any of five ways:

• When the BKGD/MS pin is low at the rising edge of reset

...

[CarlFST60L_3rd]

Thanks, I have seen the data sheet.

I was under the impression that PTA5 could be used as a standard I/O pin by disabling BDM in SOPT1. I was under the impression that the BDM was a serial interface requiring actual commands and data control, unfortunately this is not the case. It would have been great if the SOPT1 register was in flash like some of the old processors, especially on processors with such limited recources.

The data sheet details a 500nS timeout for BDM mode, and the pull up is around 30K, so now I need to come up with a way to drive a switching RF transistor (which runs a 500uS OOK data steam) and not enter BDM, and there is not space for any more components. Any idea's are welcome, we now have a complete design that is useless unless I can come up with some solutions.

[bigmac]

Hello Carl,

Another possibility might be to substitute a N-channel switching FET in place of the bipolar transistor.  I assume that the 10k resistor is currently in series with the base circuit.

A possible side effect might be a short spurious RF burst immediately after a reset.

Regards,

Mac

[CarlFST60L_3rd]

Thanks for the response Bigmac. Normally, this would be ok, though we need to use the 10K Ohm for CE and FCC requirments as this controls the Bias current for the RF oscillator. Plus, due to space constraints, we also need to directly drive an LED via a 1K Ohm resistor. If this product didnt have to fit in a 20mm x 20mm space, or run off a 20maH battery, maybe a solution could be found for using this output as, well, an output.

So it turns out this output only is pretty useless as an output for driving anything thats biased off or requires some load. So, for the first time in 10 years, we will drop a Freescale product for somthing that has a normal usable output, plus 5 other inputs.




Message Edited by CarlFST60L_3rd on 2008-08-01 03:26 AM

Message Edited by CarlFST60L_3rd on 2008-08-01 03:26 AM