Silicon Rev of 18F452

Charlie U · Posted: Tue Apr 27, 2004 4:10 pm

I'd love to turn off the added "nop" feature that was instituted quite a while back that overcomes a silicon problem in the 18F452. The latest revs of silicon, in theory, do not exhibit the problem. However, I can not find a list of target ids that correspond to the various silicon revs. The latest errata is for C0 parts with a target ID of 0x07. I have parts that are 0427. Are my parts older or newer?

Does anyone know where to find this information and could you please point me to it?

Thanks in advance.

Charlie

Haplo · Joined: 06 Sep 2003 Posts: 659 Location: Sydney, Australia

You are better off asking Microchip directly. Although I've heard they are not very helpful on questions like this...

Charlie U · Posted: Tue Apr 27, 2004 11:15 pm

I turned off the "nop" feature by editing the device file for the 18F452 using the device editor in PCWH, and recompiled. I lost about 300 bytes from my hex file, but the resulting code did not run at all. The first thing that normally happens with the code, is a message on the LCD display, but the display was just blank, not a good sign. I turned the feature back on and have moved on.

(Version 3.190)

MGP · Joined: 11 Sep 2003 Posts: 57

So Charlie... the $64 question is -- do you think the compiler is producing bad code after removing the NOP's or do you think the compiler code is fine and you still have some buggy 18F452 chips?

Just curious as I'm getting ready to do a project with the 18F452.

Charlie U · Posted: Wed Apr 28, 2004 6:31 pm

MGP,

The jury is still out on this one. My customer has started to standardize on the 18F452 for a few new products, and we have had some very good results with it on this first project. My next step will be to back off from compiler version 3.190 to 3.188 and see if it's any better. I also plan to call CCS and get their view on the subject. Right now, I am working with a pre-production board with a TQPF part on the board and no emulator adapter for it. I plan to resurrect the DIP prototype and try to sort out this a bit more with my emulator.

Regarding your project, I would not hesitate start a project with the 18F452. (I am starting another one tomorrow.) We have had no problems with the generated code except a strange printf problem (see my recent post in the 3.190 baseline thread) that popped up when I stupidly moved to 3.190.

Keep us posted on your progress and I'll post any results I have as I clean this project up.

Charlie

Guest · Posted: Thu Apr 29, 2004 4:27 am

MGP: FYI: I'm having no problem at all with the 18F452. Using 60% of RAM and ROM, and PCH 3.179. Very Happy

Before 18F452 silicon revision workarounds were implemented in the compiler I had serious trouble getting the 18F452 to work, but now everything's fine.

I'd prefer leaving the NOP's in place to be sure. If you write code up to the last 300 bytes, I think you're having the wrong processor sitting on your desk. Confused

Ttelmah · Guest

Charlie U · Posted: Thu Apr 29, 2004 6:31 am

Ttelmah,

Thanks for the reply. The date code of the parts that I have is 0344. The target ID that I was referring to, 0427, is the one that is actually read from the chip with a programmer. I wasn't certain whether to use the date code or the target ID, since I had a problem with another vendor's parts, were they were very specific in instructing us to ignore the data code and look at the chip rev. since different final assembly facilities could have overlapping data codes and silicon revs.

I'll reread the errata and hope for the best. But this still doesn't explain why the code worked with the nops and failed without them, now that we know that the chip should not exhibit the 4000h jump problem. I did not turn off the table read nops, though.

Thanks again.

Ttelmah · Guest