The Sinclair QL Forum

Hi,

All very good, but so far beyond my skills and capabilities. `HDL' I only have heard of in connection with `FPGA' boards, seems a language to setup h/w logic, with a steep learning curve for non h/w talents like me.

I was thinking of a simple logic in the `PIC' controller that would sniff on R-G-B, and whenever it decoded the 'FLASH' signal it would calculate extra colours. The logic could be dis/enabled by writing to a specific ROM address twice in succession.

My only venture so far with `PIC' was this, but I merely copied someone else's design. I plan to build a simple `PIC' programmer, that could in theory be attached to QL's SER{1,2} ports and programmed right from there. Tomas

'The only way to get out the wiring diagram would be to use a good microscope...'

Hi all,

That's exactly what I am about to do. I'm going to open up a zx8301 and have high res images taken to back annotate the design. I am initially interested in knowing the actual design of the gate array, but could ultimately, if there was demand produce a drop in replacement that could perhaps be enhanced. I will also be putting a website together at zx-83.link in the near future.

I will get back with updates soon.

K.

Hi,

Interesting a drop-in replacement to ZX8301!

I was hoping to device something slightly different, while keeping ZX8301 in place, but supplementing its logic [A] or replacing PAL chip . Currently having no knowledge of TV/RGB picture generation, so I hope the idea not being totally silly?

[A] Tomas

Tomas,
on this end of the 8301 there is not enough information to do what you intend to do - The PIC would see pixels rushing by at the sync rate - It would also see what colour the pixel would be, bit no longer why. There'd be no way to decide whether a pixel is deliberately red or red because it's currently flashing between red and some other color, for example. That's what was meant with the "missing pin". The FLASH information is lost here.

The FLASH bit sits in the screen memory and simply switches the 8301 to output another color between alternating FLASH bits, switching this behavior on and of in the FLASH interval. You'd have to look onto the data bus side of the 8301.

Tobias

Hi Tobias,

Thank you for explaining, I see the data bus carries the info needed, then.

DB{0..7}, but perhaps I need only to scan for one `FLASH' bit or not, also how do I know if in MODE 4 or 8?

Also, there is a trick of reading 16bit words over 8bit data bus, so I need to know, if lower or upper, right?

EDIT, just noticed `PCENL' connected on Iss#5 and dangling on Iss#6 boards to add to my confusion.

Tomas

Hi,

I think deeper analysis of the 8301 is required, there seems too much unknowns.

I would like a FPGA version so the HDL code could be updated to produce enhancements. But any other developments are always good to see. If you need any help please contact me.

I would be interested in the results of a microscopic investigation.

Looks kike I am back to the free Altera HDL language courses.

Hi Derek, Tobias,

Reading `Servis Manual' explains a bit about `PCENL' signal. Which is the address decode, on Iss#5 boards handled by `ZX8301', on later Iss#6 boards, handled by `HAL'.

So that brings up yet another question to my list, why `HAL' was introduced. I reckon `HAL' is kind of logic array predating programmable PAL/GALs. I guess it's capacity is hardly utilised just for three A16-A17-A14(6) address bits decode?

Mind you, I just copied it from the book, with no proper understanding.


Tomas

A HAL used to be the same thing as a PAL, but programmed in the factory (thus "hard").

The difference in handling between HAL and PAL is the same difference as between (mask-programmed) ROM and PROM.

GALs added the capability to erase and re-program the gate configuration (just like EPROM added similar capabilities to ROMs and PROMs).

Tobias

Hi,

Just thinking of the NET result, albeit implemented FPGA or PIC.

Is the PAL chip capable even of more colours, GOLD/TRUP cards bypass ZX8301+PAL chip with its own circuitry?

I think we probably need to keep stipple colours, which is a unique feature giving possibility of colour mixing, patterns, and dithering.

Tom

tofro wrote:A HAL used to be the same thing as a PAL, but programmed in the factory (thus "hard").

The difference in handling between HAL and PAL is the same difference as between (mask-programmed) ROM and PROM.

GALs added the capability to erase and re-program the gate configuration (just like EPROM added similar capabilities to ROMs and PROMs).

Tobias

Hi Tobias,

Can a HAL be read or is there a security bit.