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Re: Z80 based wearable

From: Eric Laforest <>
Date: Mon, 1 May 2000 19:58:14 -0400

On Mon, May 01, 2000 at 05:20:07AM -0700, Doug Sutherland thus spake:
> Eric, 
> 
> You should look into the Patriot Scientific PSC1000 processor.
> It is a low cost chip that supports asm, c, forth, and java. 
> Interestingly, the stack based machine looks just like a java
> virtual machine, only the opcodes are different. They have 
> a bytecode translator that allows java to run natively. 
> www.ptsc.com
> 
> Doug

I know of it, but it wouldn't be appropriate for several reasons:

- Software: the only devel envs are separate (host computer based)
  most likely cost a fortune, and are closed source.
  The kit I will order comes with a self-contained cmForth
  engine with source and is minimal and comprehensible.
  The kit is 150$US too, all inclusive, if a little bare.
  (AFAIK: CPU, RAM, ROM (cmForth inside), UART and a floppy/manual)
  With a little support added for a Twiddler and a Matrix Orbital
  display, it becomes a self-contained devel env.
  Add mass-storage in the form of PSX memory modules (found the specs
  today at: http://www.execpc.com/~halkun/PSX/index.html
  and it seems doable) and I get a complete system.

- Hardware: it's a *complex* chip..by comparison, the RTX2000 is
  *so* clean, it's almost perfect.
  I used to think the MuP21 and/or F21 had the title of
  "Most Perfect CPU", but trolling through 5 years of mailing list
  archive has unearthed many, many uglies...
  The RTX2000 may very well have it's own flaws, but after perusing
  available docs, it seems flawless by comparison.
  The RTX2000 also has a single-cycle 16x16->32 multiplier, which
  fits my DSP ideas, and has extravagant eval and return stacks
  (256 deep each).
  It also tickles me that the interrupt service latency of the
  RTX2000 is a constant 400ns (yep..*nano*-seconds) although I
  can't think of any application I would do that needs that.
  (It's icing on the cake: should side-step a few ISR timing issues.)

Basically, I think the RTX2000, although "obsolete" is the solution
for the goal of homebrewing a computer of significant power
(RTX2000 runs at 10MHz, and can pack multiple instructions per word
 for many cases..it's also a single-cycle CPU (2 cycles if memory access))
and that will also be compact enough to become a wearable.

The specs for a near-identical chip (RTX2010RH, has some floating point
and minor changes) can be found by searching for RTX 2000 on 
www.intersil.com. (It's all I could find...my kingdom for the 
original manuals!)

Eric LaForest

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