[Coco] Coco compatible monitors...

[gene heskett]

On Tuesday, July 05, 2011 11:23:07 AM John Kent did opine:

> Hi Gene
> 
> On 6/07/2011 12:04 AM, gene heskett wrote:
> > On Tuesday, July 05, 2011 09:50:20 AM John Kent did opine:
> >> Terasic DE1 is here:
> >> http://www.terasic.com.tw/cgi-bin/page/archive.pl?No=83
> > 
> > No doubt capable, but way too big to hide in a cc3 unless the whole
> > coco was emulated.
> 
> You've seen Gary's CoCo3FPGA, surely .... It's been mentioned on the
> list often enough.
> It emulates the entire CoCo3 and uses a modern LCD display and PS/2
> keyboard.
> 
> You'd have to design your own PCB for the GIME chip replacement.
> The point was that with the CoCo3 design there should be a GIME
> component to the design that could be separated off an put into it's own
> smaller FPGA. That is if Gary makes his CoCo3FPGA open source, which I
> think he plans to in the not to distant future.
> 
That, or a reasonable fee, will be the make or break for me.  I have a 
couple coco3's I can salvage a case from, one of which is Dennis Scala's 
original machine, with a very noisy gime in it.

That keyboard in Joel's conversion sure looks nice, I wonder where did it 
come from?

> > That maybe could be hidden under the keyboard.  With a vga output no
> > less.
> > 
> > Would I have to run the development system on windows?  If yes, no
> > deal.
> 
> The Spartan 3 starter board does have expansion connectors, but whether
> there are enough pins for the PLCC 68 pin chip I'm not sure. Some of the
> pins on some of the connectors are shared with the on board SRAM address
> and data bus, but if you disabled the on board RAM you could use them.
> 
> You'd still need the 3.3V to 5V bus switches to do the level conversion.
> 
> > the development stuff for xilinx is nearly free, so that, and custom
> > made breakout cables might add a lot of functionality to a coco3.
> 
> Xilinx have webpack ISE which is free to download. It's about 2-3GB.
> Altera have free Quartus II development software which is a similar
> size. You'd have to register with Xilinx or Altera to download them.

ah, that explains why the stuff I grabbed was just a few megabytes.
 
> You'd have to learn verilog or VHDL hardware description languages,
> although there might be a schematic capture option too, although that is
> not portable between the two vendors I don't think. VHDL & verilog are
> similar to normal pogramming languages in that they have standard
> control structures such as case/when and if/then/else. The difference is
> that you are generating a hardware description with them rather than a
> set of instructions. Case/when for instance is analogous to a decoder
> chip, or multiplexer, although the inputs and outputs are not restricted
> to a single bit.
> 
> Micro computers are essentially time division multiplexed logic using
> the ALU to perform the operations sequentially. With a hardware
> description language like verilog or VHDL you are actually defining a
> hardware configuration for the FPGA logic that operates in parallel with
> all the other hardware.  It's a like connecting all the ALU operations
> of a micro computer end to end to operate in parallel with the variables
> being hardware registers in between the various stages.
> 
> VHDL and Verilog allow you to define components or entities that can be
> instantiated as many times as you like, or as many times as fits in the
> chip. So for instance if you define a 6850 ACIA you can instantiate it
> (i.e. produces copies of it from the definition) as many times as you
> like in your design. You are of course limited by the amount of logic
> available in the FPGA and you have to connect them together in your
> design.

Well, if the water doesn't get too high...
 
> > For about 90 bucks and some time, that looks like a usable gizmo.
> > IIRC,
> 
> There are only 40 pins available on the XuLA boards and a number of them
> are allocated to supply rails, clocks and resets and so on. Some of the
> pins are inputs only and again you'd need 3.3V to 5V bus switches.
> 
> >> There are a number of other Xilinx boards from Digilent Inc. and
> >> others.
> >> 
> >> Digilent is to Xilinx what Terasic is to Altera.
> >> 
> >> There are pictures of the FPGA boards I use on my FPGA page:
> >> http://members.optusnet.com.au/jekent/FPGA.htm
> > 
> > bookmarked.
> > Cheers, gene
> 
> Hope that helps explain things.

Considerably, thanks John.


Cheers, gene
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