In SX Microcontrollers, SX/B Compiler and SX-Key Tool, dkemppai wrote:

[quote="pjv"]
Hi Dan;

Well, how do you like this one for coincidences...... Yesterday I posted that I never had a problem programming or debugging SX48s at 3 volts. Today the story has changed, and while I can program them fine, I had some strange results in debugging as well as running programs. But not consistently.

So my solution now is to have the very first instuction after the reset jump from $FFF be a bank$10 statement to initialize the FSR properly. And why I had not knowingly run accross this situation before, is that I almost always start my programs with a standard template, and that happens to have the requisite bank instruction early enough to point at the desired memory and yield proper results.

Experiment with this and try it Dan, it might be the answer for you, and please do let us know how you make out!

Cheers,

Peter (pjv)[/quote]Thank you! I knew I wasn't crazy! Every single time I try to run these chips below 5 volts, I get into trouble. They run flawlessly at 5, but below that, they get squirrly. A lot of times I can't figure out how I ended up fixing it.  Also, as for the documentation, watch out with all of the reset states. There are many errors in there...   ...learned that the hard way. 
 

Anyway, I tried your suggestion, and it didn't fix my issue. I still can't debug at, or even RUN at 3.3 volts. I tried lowering the system voltage once the chip was up and running, and the debugger just stopps at 4.09 volts. Below that, nothing. Above that, everything works as expected. I was watching the OSC2 pin with a scope, and it appears that line never gets to a high enough voltage level to let the debugger know that it's ready to run. 

 

The only thing I have tied to the SX on this board is the SX Key, a 10K MCLR pullup resistor, and 4 SMD 0603 bypass capacitors and one SPI DAC. I've built FPGA boards (150Mhz), Optical communications circuits, Pic boards, SMD RF transmitters, high precision analog circuits, and hardwired logic, and I've never ever had as much trouble with anything as this stupid little chip. I'm going to very serously start looking at some of the other MCU's out there. This thing is just to difficult to get to run at 3.3 volts or under. Unfortunatley for this project, I'm married to this chip. 

 

 

-Dan

 

 

P.S. As for the 1K Ohm to ground, I replaced the chip, and that fixed the "VPP Generation failed" error. But, I'm still having problems getting this chip to do anything below 5 volts. So, at least 1 bad SX out of the box.

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