Re: MISC-d Digest V97 #6

[jfox@xxxxxxxx (Jeff Fox)]

Dear MISC readers:

Andrew Sieber <asieber@usa.net> asked:

>Dear MISC readers,
>I've got a P21 system sort of cobbled together on a breadboard, and it
>doesn't appear to be working (yet.)  I want to make sure I'm doing this
>right:
>P21Forth version 1.02 displays "P21Forth" on the video display
>immediately after the processor is reset, without waiting for keyboard
>input, doesn't it?  I'm using the slow.rom image file burned into an
>eprom chip, and the system is based on Dr. Ting's P21A5 PCB schematic
>that he put in the MuP21 Manual.  I have not yet hooked a keyboard to
>the system, and am simply trying right now to apply power and get it to
>put "P21Forth" on the screen so I can know that the system is working
>and thus I strung all my wires correctly.  But when I apply power, I get
>no video out.  Before I go troubleshooting, I want to make sure it's
>supposed to actually be generating video even with no keyboard attached.
>
>--Andrew
>asieber@usa.net

P21A5? Which board is that?  P21Forth 1.02 comes in three versions.  One
for simulator, one for the development system (with the i/o chip I have
on mine) and one for the kit board with the parallel port.  I don't recall
the version number of the boards.  It does not run on the latest board
with only the 82C51 serial port i/o.  I did start debugging a port to
that board but never finished it.

P21Forth 1.01 booted w/ either serial or parallel i/o based on what
it found connected at boot.  P21Forth 1.02 booted in serial i/o mode on
the parallel port.  Both place "P21Forth" on the video display before 
they read input.

I would recommend first debugging using the simple OK demo rom.  It is
a little easier to get 2K of code up and running than 16K of code.  Also
OK has much less off page program access and therefore seems to run over
a wider voltage range than P21Forth.  As the documentation for P21Forth
says it will run from about 4.9 to 6.x volts depending on the brand of
drams used.  The ones that came with the kit would not run above 5.4. 
The P21Forth documentation recommends running at 5.8 to 6.0 if you 
can as the increased voltage will reduce video noise.

    Jeff Fox
    jfox@dnai.com              Ultra Technology Inc.
    jeff@itvcorp.com           the iTV Corporation
    http://www.dnai.com/~jfox/