Hi Christopher,

You've just hit the "Its _ALMOST_ compatible" bug :)

Not to worry - It is simple to fix (something like this got me as well).

Basically the newer PICs with Analogue converters or comparators all seem to
start up with them enabled. You have to disable them and then you have
access to the pins as digital I/O just like the 'F84.

Have a look at section 9.0 (page 57) of the datasheet. I think that if you
set the CMCON register (0x01F) to 0xFF you should get digital pins. I
haven't tested this as I use C and just tell it to do it for me :)

Oh, another trick with these if you only want OUTPUTs, and some Analogue
inputs is to leave the analogue inputs enabled and use the TRIS register to
control if a pin is a digital output or an analogue input. Probably not that
useful on a '628 with comparators, but works great on a '876/7 where you
have an ADC. Yes, there are settings to control which pins are analogue and
which are digital, but you can't get all the combinations you might want..

Good luck
Ash.

---
Ashley Roll
Digital Nemesis Pty Ltd
www.digitalnemesis.com
Mobile: +61 (0)417 705 718




> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Christopher Tyler
> Sent: Monday, 10 September 2001 6:53 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC]:16F628 from 16F84
>
>
> Hi all
> I am working on a project that was using the 16F84. On this chip, the
> program runs perfectly. But we are trying to cut our costs. Someone
> suggested we use the 16F628 instead. I had a look at the data
> sheets on
> the 16C628, and they seem mostly the same. So I moved to the new
> chip. But now the program doesnt work anymore.
> The problem is when simulating using MPLAB. U can't change
> the state of
> any of the  "pins" on PORTA. I have tried using Pin Stimulis Files,
> Asynchronis Stimulis, etc. But none of the pins ever go high. Port B
> works
> fine.

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