The Sinclair QL Forum

QViewStu wrote:Not sure if that board was tested working but the GAL is the wrong way round unless my eyes deceive me…

I removed the GAL and read it i on my Programmer, it look to have not been powered on with the GAL in the wrong orientation.

QViewStu wrote:That looks like a stunt Minerva without the legs bent out to fit the PCB socket ;-0

There is a way to not have the Eprom legs bent out, just needs the PCB altered to suit.

OMG, I've just realised the EPROM in the photo from QLWorld is in upside down

Silvester wrote:OMG, I've just realised the EPROM in the photo from QLWorld is in upside down

I saw the screen and suspected it came from a magazine or print photo so it was an publicity Minerva I guess these days it would be an Influencer Minerva

First post!

Here's a PDF of the PCB layout from the original sources, before the RiscPC went belly up. Planning to fix it tomorrow. Stu did send me a disassembly of the GAL logic, which I've switched around and commented, but it's unchecked so I'll leave posting that until I'm a bit surer. can't find the original source for that...

Cheers

Jonathan

QJumpJon wrote:First post!

Hi Jonathan, would be nice to read more about the Pointer I/F and Wman in a separate thread. When it was designed, how it would be designed this way and why has it changed to use secondary windows just inside the primary window.

Hi,

The PCB layout file is very interesting.

I am in the process of drawing the PCB schematic in KiCad, with a view to reproduce the Minerva MKII.

Are there any copyright restrictions?

I do not suppose the Minerva Mk I PCB layout is available?

Derek_Stewart wrote:Hi,

The PCB layout file is very interesting.

I am in the process of drawing the PCB schematic in KiCad, with a view to reproduce the Minerva MKII.

Are there any copyright restrictions?

I do not suppose the Minerva Mk I PCB layout is available?

Well, I originally drew it, but then TF took Minerva over so technically I guess it's Tony's shout these days. Is he still about? I'm fine with it being open source, myself.

I've attached my reverse engineering of the schematic (drawn in Inkscape!), along with the images posted above. Note that GAL pin 7 is tracked to both Vcc and Gnd, so will cause a short unless one track is cut. From the GAL logic it looks like Gnd is the correct one to cut for normal operation: that's the one on the component side.

Pretty sure the MK I is on the RiscPC, assuming I resurrect it I'll post the result.

Cheers

Jonathan

Derek_Stewart wrote:There is a way to not have the Eprom legs bent out, just needs the PCB altered to suit.

Really? Pretty sure we "wouldn't do it just just for fun"... (points for getting the quote there)

Cheers

Jonathan

Silvester wrote:

Pr0f wrote:so looking at those stripped circuit boards - the chip under the ROM was a 13 Input NAND gage - so presumably used to do the finer address decoding for the SDA / SCL

Using a 7430 (8 input NAND) would have been enough, SGC allows direct access through to $BF80-BFFF.

The 74LS133 was (I believe) needed: all bar 2 inputs are certainly used. The GAL as it stands decodes A15+A14+A5+A4, of which only A15 goes to the LS133. I vaguely recall some clash with other hardware which led to the use of A5+A4 on the GAL to give us some choices of where to put the I²C access address. I could have used an LS30 by putting more decode in the GAL on spare pins, but as we needed an LS anyway it probably made more sense to use most of the LS133 and keep back spare GAL pins in case of future fixes or features. The logic for pin 13 is certainly a bit odd, there must have been a timing issue, but I've no idea when that was discovered!

I think the [Super] Gold Card interfered with correct operation, don't recall how...

Cheers

Jonathan

RalfR wrote:Hi Jonathan, would be nice to read more about the Pointer I/F and Wman in a separate thread. When it was designed, how it would be designed this way and why has it changed to use secondary windows just inside the primary window.

Can't promise I can remember much about it! But it's worth a go...

Cheers

Jonathan