The Sinclair QL Forum

Hi, I have a bit of knoledge on programing gals, not to much, but enought to program by myselft a gal for memory expansion.
If you provide me the schematics, I can do code to use a spare pin as enable/disable.

I will also be interested in 1 of this PCB if yet available.

The only problem with your design is i'm not sure if is posible to reprogram it without desolder from the PCB.

aalea wrote:Hi, I have a bit of knoledge on programing gals, not to much, but enought to program by myselft a gal for memory expansion.
If you provide me the schematics, I can do code to use a spare pin as enable/disable.

I will also be interested in 1 of this PCB if yet available.

The only problem with your design is i'm not sure if is posible to reprogram it without desolder from the PCB.

Someone else is also about to do the same thing at the moment, so probably silly having 2 people aiming at the same goal. It's not a massive issue that the GAL is not socketed as only the one board is currently made up. I need to get it changed due to the missing connection and will also make other changes at the same time.

The schematics are exactly the same as the through hole version. PM me.

In addition to spare input pin (for enable switch) it will require RESET (to clock enable/disable condition through only on reset). Something I forgot to mention Chr$

aalea if it is OK for you to create JED for changes required please do. It'll probably be quicker than it'll take me to come up to speed

Silvester wrote:In addition to spare input pin (for enable switch) it will require RESET (to clock enable/disable condition through only on reset). Something I forgot to mention Chr$

A connection to RESET on the CPU you mean? That shouldn't be a problem.

Chr$ wrote:A connection to RESET on the CPU you mean? That shouldn't be a problem.

Yes, probably to pin 1.

I was trying to think if there was a way to force into 128K mode by doing quick double reset. Probably impossible to reliably detect

Perhaps one of the reset management IC's that are available - as these cater for resetting on voltage drop outs, pressing a reset button and so forth - but are able to distinguish between a button reset and a power interruption
related reset

Chr$ wrote:

Silvester wrote:In addition to spare input pin (for enable switch) it will require RESET (to clock enable/disable condition through only on reset). Something I forgot to mention Chr$

A connection to RESET on the CPU you mean? That shouldn't be a problem.

I don't think that this will be necesary.
You should only change the enable switch with the computer power off, if you do with it on, the worse can happend is that the QL hang and need a reset.

OK, In the ZIP file attached there is the GAL program with a Enable pin. (a .JED file for direct program the gal and a .PLD program for compile with winculp)

To work as a memory upgrade, PIN 2 should be conected to 5V, if it's conected to 0V, the memory expansion will be disable.

You can use a SPDT switch with 5V, PIN2, 0V conections,

or tie the pin 2 to VCC with a 10K resistor, and a jumper between PIN2 and GND, with the jumper the interface will be disable, without junper it works as aditional 512Kb.

I can not test it, but if you previously use the .JED file from this post: viewtopic.php?f=2&t=877&start=70#p7928 this should work also.

There is no reset pin, so you should only change it with QL power off.

aalea wrote:OK, In the ZIP file attached there is the GAL program with a Enable pin. (a .JED file for direct program the gal and a .PLD program for compile with winculp)

To work as a memory upgrade, PIN 2 should be conected to 5V, if it's conected to 0V, the memory expansion will be disable.

You can use a SPDT switch with 5V, PIN2, 0V conections,

or tie the pin 2 to VCC with a 10K resistor, and a jumper between PIN2 and GND, with the jumper the interface will be disable, without junper it works as aditional 512Kb.

I can not test it, but if you previously use the .JED file from this post: viewtopic.php?f=2&t=877&start=70#p7928 this should work also.

There is no reset pin, so you should only change it with QL power off.

I'll try that out with another of my slightly wrong PCBs.

aalea wrote:OK, In the ZIP file attached there is the GAL program with a Enable pin. (a .JED file for direct program the gal and a .PLD program for compile with winculp)

To work as a memory upgrade, PIN 2 should be conected to 5V, if it's conected to 0V, the memory expansion will be disable.

You can use a SPDT switch with 5V, PIN2, 0V conections,

or tie the pin 2 to VCC with a 10K resistor, and a jumper between PIN2 and GND, with the jumper the interface will be disable, without junper it works as aditional 512Kb.

I can not test it, but if you previously use the .JED file from this post: viewtopic.php?f=2&t=877&start=70#p7928 this should work also.

There is no reset pin, so you should only change it with QL power off.

That seems to work! I didn't have a keyboard attached but booting with Minerva correctly shows 128k or 640k depending on how it's switched. I also turned the extra RAM off and attached an external 512k Expanderam, which was fine (and definitely didn't work with the internal RAM enabled). I will test further.

Then I'll get some updated PCBs made, with:

- GAL pin 16 connection to CPU pin 31 instated.
- More space around the GAL so that sockets can be used if so preferred, without coming too close to the caps.
- Longer solder pads for the GAL, so that it's easier to solder those J shaped PLCC pins that disappear underneath the chip.
- Add some kind of appropriately placed right-angled switch and the required connections to pin 2 of the GAL and 5v/GND.
- Remove the unnecessary rows of header pins next to the space for the CPU.

It'll be great with the switch, not just because you can turn it off to use anything with external RAM but by extension, because the CPU sockets are a bit naff it means you can install it and just leave it there indefinitely.