#isa — Public Fediverse posts

https://www.europesays.com/britain/44736/ £7,500 invested in Rolls-Royce shares at the start of the new ISA year is now worth… #investors #ISA #RollsRoyce #StocksAndSharesISA

https://www.europesays.com/fi/252601/ Kerttu Rissanen teki harvinaisen julkaisun: Tältä näyttää hänen isänsä! #äiti #Celebrities #Entertainment #euroviisut #FI #Finland #Finnish #isä #Julkkikset #KerttuRissanen #mummu #Perhe #Suomi #Turku #viihde

https://www.europesays.com/fi/252112/ Julkkiskokki Teemu Laurellin ex-rakas Mirella Merivirta: Pahin pelko kävi toteen #Entertainment #ero #FI #Finland #Finnish #isä #MirellaMerivirta #Perhe #suhde #Suomi #TeemuLaurell #vauva #viihde #yksinhuoltajuus

https://www.europesays.com/es/558692/ Alberto Isla se casa por tercera vez: así es la nueva vida del ex de Isa Pantoja #alberto #casa #Celebrities #Entertainment #Entretenimiento #ES #España #ex #Famosos #isa #isla #nueva #pantoja #Spain #tercera #vez #vida

Viele 🚗 🚚 🚗 treffen sich gerade auf der A3: Nürnberg -> Passau, zwischen 3.0 km hinter Spitzig Berg und 3.6 km vor Kühberg und blockieren die #Autobahn.

Es könnte sein, dass sie heute die #EU-weit verpflichtende Installation eines intelligenten, übersteuerbaren Geschwindigkeitsassistenten in alle #Neufahrzeuge fordern. Das könnte langfristig die Zahl der #Verkehrstote​n um 20% reduzieren. Viel weniger Autos hätten #Totalschaden. 🚗⚠️ #Verkehrssicherheit #ISA (Quelle: ETSC)

I loved ❤️ the TV series:

“Halt And Catch Fire”, Scott Robinson (https://unstack.io/halt-and-catch-fire).

Via HN: https://news.ycombinator.com/item?id=48162468

#ComputerHistory #CPU #Hardware #RetroComputing #ISA #HCF #HaltAndCatchFire #TV #TVSeries #IBM #Motorola

I loved ❤️ the TV series:

“Halt And Catch Fire”, Scott Robinson (https://unstack.io/halt-and-catch-fire).

Via HN: https://news.ycombinator.com/item?id=48162468

#ComputerHistory #CPU #Hardware #RetroComputing #ISA #HCF #HaltAndCatchFire #TV #TVSeries #IBM #Motorola

I loved ❤️ the TV series:

“Halt And Catch Fire”, Scott Robinson (https://unstack.io/halt-and-catch-fire).

Via HN: https://news.ycombinator.com/item?id=48162468

#ComputerHistory #CPU #Hardware #RetroComputing #ISA #HCF #HaltAndCatchFire #TV #TVSeries #IBM #Motorola

I loved ❤️ the TV series:

“Halt And Catch Fire”, Scott Robinson (https://unstack.io/halt-and-catch-fire).

Via HN: https://news.ycombinator.com/item?id=48162468

#ComputerHistory #CPU #Hardware #RetroComputing #ISA #HCF #HaltAndCatchFire #TV #TVSeries #IBM #Motorola

I loved ❤️ the TV series:

“Halt And Catch Fire”, Scott Robinson (https://unstack.io/halt-and-catch-fire).

Via HN: https://news.ycombinator.com/item?id=48162468

#ComputerHistory #CPU #Hardware #RetroComputing #ISA #HCF #HaltAndCatchFire #TV #TVSeries #IBM #Motorola

Viele 🚗 🚚 🚗 treffen sich gerade auf der A3: Nürnberg -> Passau, zwischen 3.0 km hinter Spitzig Berg und 3.6 km vor Kühberg und blockieren die #Autobahn.

Es könnte sein, dass sie heute die #EU-weit verpflichtende Installation eines intelligenten, übersteuerbaren Geschwindigkeitsassistenten in alle #Neufahrzeuge fordern. Das könnte langfristig die Zahl der #Verkehrstote​n um 20% reduzieren. Viel weniger Autos hätten #Totalschaden. 🚗⚠️ #Verkehrssicherheit #ISA (Quelle: ETSC)

"Thanks bro, Isa mad helpful in these trying times"

https://piefed.social/c/historymemes/p/2059898/thanks-bro-isa-mad-helpful-in-these-trying-times

"Thanks bro, Isa mad helpful in these trying times"

https://piefed.social/c/historymemes/p/2059898/thanks-bro-isa-mad-helpful-in-these-trying-times

"Thanks bro, Isa mad helpful in these trying times"

https://piefed.social/c/historymemes/p/2059898/thanks-bro-isa-mad-helpful-in-these-trying-times

"Thanks bro, Isa mad helpful in these trying times"

https://piefed.social/c/historymemes/p/2059898/thanks-bro-isa-mad-helpful-in-these-trying-times

"Thanks bro, Isa mad helpful in these trying times"

https://piefed.social/c/historymemes/p/2059898/thanks-bro-isa-mad-helpful-in-these-trying-times

https://www.europesays.com/fi/245728/ Kari Hietalahti: Harvinainen yhteiskuva pojan kanssa #AikuinenLapsi #Entertainment #FI #Finland #Finnish #HarvinainenKuva #HarvinainenYhteiskuva #HarvoinNähty #ikä #ikäero #isä #IsäJaPoika #IsäPoikaSuhde #KariHietalahti #kuva #lapsi #näyttelijä #Perhe #perhesuhteet #poika #SakariHietalahti #Suomi #viihde #yksityiselämä

https://www.europesays.com/es/541297/ el historial amoroso de Omar Montes #amoroso #Celebrities #Entertainment #Entretenimiento #ES #España #Famosos #hijos #historial #isa #Madres #montes #omar #Spain #tres

PDS – the Programmers Development System – Part 2

This series of posts looks at the Programmers Development System (PDS).

• Part 1 – Introduction, background and some initial reverse engineering.
• Part 2 – A closer look at the PC ISA Interface card.

Having now got a bit of an idea of how the PDS appears to work in my previous post (PDS – the Programmers Development System) I’m now taking another look at the PC interface and starting to think about the possibility of recreating the system.

The PC Interface

Having decided I couldn’t rely on the schematic on the CPC wiki, I’ve taken the printout-versions of the PCB traces and started tracing them through to see what is really going on. It was greatly helped by the PCB view that can be found here: https://lemmings.info/pds-programmers-development-system/

Of course, I am assuming here that the remade PC card does actually work.

It turns out the ISA to Intel 8255 part was fine, including the address decoding, but the three 8255 IO ports, through the octal line buffers, to the two PDS links are fundamentally missing some key links.

Essentially the three 74LS244s are configured for half in A->Y form and half in Y->A. The three IO ports (PORT A, B, C) are also split in half. This means that most of this circuit is working in 4-bit chunks.

The high level linkages are shown below.

So here we can see how the A halves of each of the 244s handles OUTPUT and the B halves handle INPUT. We can also see that U5 (sticking with the original schematic numbering for now) handles the control signals, U4 is D4-7 and U3 is D0-3. PORTC drives U5 and thus also handles all control signals.

We can also see that the data lines are now fully bidirectionally connected so that each can be connected to an OUTPUT or an INPUT depending on the state of the PC2 line. PORTB handles the OUTPUT and PORTA is the input.

The control signals are still mirrored as determined in the first part, but now we can see that some are OUTPUTs and some are INPUTs. The mappings from PC0-7 through to the link pins is shown below (note I’ve reverted to using the same PDS connector pin numbers as the ZX Spectrum schematic in the diagram above and table below).

There are two swapped pairs of connections, two common, and one unique to each.

As mentioned previously, the ZX Spectrum interface does not connect to pins 9,11,13,15 so that implies to me that it would not work out of link 2 without remapping in the software for the alternative pinout.

From working through the ZX Spectrum monitor code in part 1, we can infer the following functions:

• Pin 3 (OUT): PC to Target CLOCK
• Pin 5 (IN): Target to PC CLOCK/ACK

We can also note the following:

• Pin 11 (OUT): Direction based on PC2. HIGH = PC to Target; LOW = Target to PC

From this point I can now fully recreate the schematic and start to think about recreating the PCB.

The PC Hardware

One slight sticking point in remaking the PCB was getting useful dimensions for an XT era ISA card. Two useful references I found were:

• The ISA Spec can be found as part of the PC XT Technical Reference: https://bitsavers.org/pdf/ibm/pc/xt/6361459_PC_XT_Technical_Reference_Apr84.pdf
• Researched 8-bit ISA card dimensions: https://www.andavno.com/?p=87

The actual spec wasn’t massively useful to me. I don’t know if the ends of cards was slightly different in PC XT systems, but it doesn’t seem to match the photos of the PDS PC card. The second link was very well researched and complete however, so I went with that.

One compromise though was trying to keep the card within a 100x100mm footprint, so I’ve not extended completely to what I believe will be long enough to have an end plate.

The Schematic

The updated schematic is shown above. I’ve added a few things I’d expect to see on a modern design – additional 100nF capacitors (one for each IC), and a resistor network to pull up all unused inputs to the 74LS04.

I originally went with the ZX Spectrum version of the 16-way connector, but then when it came to assigning footprints, to get a right-angled IDC connector meant pin one was now in the wrong place, so I had to revert to the alternative pin numbering as per the original schematic.

The PCB

I’ve followed the original layout used on the PC card remake as far as possible, reasoning that the person who did this almost certainly knows a lot more about electronics than I do.

One thing I wasn’t sure about was a GND fill. I initially created a fill zone, but then decided I’d follow the original lead and use explicit GND connections. If someone advises that a fill will be better then it is pretty trivial to add in.

Other points to note:

• A already mentioned I’ve kept this within the 100x100mm footprint. This leaves two unknowns: will it be tall enough to be useful; and will it extend to the edge of a PC case?
• The two connectors extend beyond the edge of the PCB, so they hopefully will be available at the edge of a PC.
• The dimensions are such that more of the PCB is off to the right compared to the photos of the remade board I’ve seen.

This will do for now, but I think it is highly likely there will need to be some physical adjustments for this to be usable.

Conclusion

I believe I’ve got an accurate schematic for the board based on the photos available and I now have design for a candidate PCB. The problem is that I don’t know anything about what the software is expecting when it drives the Intel 8255 to work the PDS interface.

There is also the small matter of needing an ISA bus in a PC…

I’m hoping to get these boards published somewhere but right now, I’m not clear what the licensing issues would be. These boards are not available anymore, but at some point this was a company’s IPR.

For now, I’ll keep blogging observations and see what the interest is.

Next up will be some remake of the target PCBs.

Kevin

PDS – the Programmers Development System – Part 2

This series of posts looks at the Programmers Development System (PDS).

• Part 1 – Introduction, background and some initial reverse engineering.
• Part 2 – A closer look at the PC ISA Interface card.
• Part 3 – Remaking the target interfaces.

Having now got a bit of an idea of how the PDS appears to work in my previous post (PDS – the Programmers Development System) I’m now taking another look at the PC interface and starting to think about the possibility of recreating the system.

The PC Interface

Having decided I couldn’t rely on the schematic on the CPC wiki, I’ve taken the printout-versions of the PCB traces and started tracing them through to see what is really going on. It was greatly helped by the PCB view that can be found here: https://lemmings.info/pds-programmers-development-system/

Of course, I am assuming here that the remade PC card does actually work.

It turns out the ISA to Intel 8255 part was fine, including the address decoding, but the three 8255 IO ports, through the octal line buffers, to the two PDS links are fundamentally missing some key links.

Essentially the three 74LS244s are configured for half in A->Y form and half in Y->A. The three IO ports (PORT A, B, C) are also split in half. This means that most of this circuit is working in 4-bit chunks.

The high level linkages are shown below.

So here we can see how the A halves of each of the 244s handles OUTPUT and the B halves handle INPUT. We can also see that U5 (sticking with the original schematic numbering for now) handles the control signals, U4 is D4-7 and U3 is D0-3. PORTC drives U5 and thus also handles all control signals.

We can also see that the data lines are now fully bidirectionally connected so that each can be connected to an OUTPUT or an INPUT depending on the state of the PC2 line. PORTB handles the OUTPUT and PORTA is the input.

The control signals are still mirrored as determined in the first part, but now we can see that some are OUTPUTs and some are INPUTs. The mappings from PC0-7 through to the link pins is shown below (note I’ve reverted to using the same PDS connector pin numbers as the ZX Spectrum schematic in the diagram above and table below).

There are two swapped pairs of connections, two common, and one unique to each.

As mentioned previously, the ZX Spectrum interface does not connect to pins 9,11,13,15 so that implies to me that it would not work out of link 2 without remapping in the software for the alternative pinout.

From working through the ZX Spectrum monitor code in part 1, we can infer the following functions:

• Pin 3 (OUT): PC to Target CLOCK
• Pin 5 (IN): Target to PC CLOCK/ACK

We can also note the following:

• Pin 11 (OUT): Direction based on PC2. HIGH = PC to Target; LOW = Target to PC

From this point I can now fully recreate the schematic and start to think about recreating the PCB.

The PC Hardware

One slight sticking point in remaking the PCB was getting useful dimensions for an XT era ISA card. Two useful references I found were:

• The ISA Spec can be found as part of the PC XT Technical Reference: https://bitsavers.org/pdf/ibm/pc/xt/6361459_PC_XT_Technical_Reference_Apr84.pdf
• Researched 8-bit ISA card dimensions: https://www.andavno.com/?p=87

The actual spec wasn’t massively useful to me. I don’t know if the ends of cards was slightly different in PC XT systems, but it doesn’t seem to match the photos of the PDS PC card. The second link was very well researched and complete however, so I went with that.

One compromise though was trying to keep the card within a 100x100mm footprint, so I’ve not extended completely to what I believe will be long enough to have an end plate.

The Schematic

The updated schematic is shown above. I’ve added a few things I’d expect to see on a modern design – additional 100nF capacitors (one for each IC), and a resistor network to pull up all unused inputs to the 74LS04.

I originally went with the ZX Spectrum version of the 16-way connector, but then when it came to assigning footprints, to get a right-angled IDC connector meant pin one was now in the wrong place, so I had to revert to the alternative pin numbering as per the original schematic.

The PCB

I’ve followed the original layout used on the PC card remake as far as possible, reasoning that the person who did this almost certainly knows a lot more about electronics than I do.

I’ve also tried to keep the connectors as close to the positions on the original as far as possible, whilst still keeping within the 100x100mm PCB total size.

One thing I wasn’t sure about was a GND fill. I initially created a fill zone, but then decided I’d follow the original lead and use explicit GND connections. If someone advises that a fill will be better then it is pretty trivial to add in.

Other points to note:

• A already mentioned I’ve kept this within the 100x100mm footprint. This leaves two unknowns: will it be tall enough to be useful; and will it extend to the edge of a PC case?
• The two connectors are roughly in the same horizontal position as the original card. They seem comparable to where the pins align with the edge connector anyway. An earlier iteration had them extending beyond the PCB, but I’ve redesigned it to mirror the original card.
• The dimensions are such that more of the PCB is off to the right compared to the photos of the original or the remade board I’ve seen.
• I’ve not been able to include mounting holes in any useful position whilst retaining the 100x100mm footprint.

The current dimensions of the above PCB are shown below.

This will do for now, but I think it is highly likely there will need to be some more physical adjustments at some point for this to be usable.

Conclusion

I believe I’ve got an accurate schematic for the board based on the photos available and I now have design for a candidate PCB. The problem is that I don’t know anything about what the software is expecting when it drives the Intel 8255 to work the PDS interface.

There is also the small matter of needing an ISA bus in a PC…

I’m hoping to get these boards published somewhere but right now, I’m not clear what the licensing issues would be. These boards are not available anymore, but at some point this was a company’s IPR.

For now, I’ll keep blogging observations and see what the interest is.

Next up will be some remake of the target PCBs.

Kevin

PDS – the Programmers Development System – Part 2

This series of posts looks at the Programmers Development System (PDS).

• Part 1 – Introduction, background and some initial reverse engineering.
• Part 2 – A closer look at the PC ISA Interface card.

Having now got a bit of an idea of how the PDS appears to work in my previous post (PDS – the Programmers Development System) I’m now taking another look at the PC interface and starting to think about the possibility of recreating the system.

The PC Interface

Having decided I couldn’t rely on the schematic on the CPC wiki, I’ve taken the printout-versions of the PCB traces and started tracing them through to see what is really going on. It was greatly helped by the PCB view that can be found here: https://lemmings.info/pds-programmers-development-system/

Of course, I am assuming here that the remade PC card does actually work.

It turns out the ISA to Intel 8255 part was fine, including the address decoding, but the three 8255 IO ports, through the octal line buffers, to the two PDS links are fundamentally missing some key links.

Essentially the three 74LS244s are configured for half in A->Y form and half in Y->A. The three IO ports (PORT A, B, C) are also split in half. This means that most of this circuit is working in 4-bit chunks.

The high level linkages are shown below.

So here we can see how the A halves of each of the 244s handles OUTPUT and the B halves handle INPUT. We can also see that U5 (sticking with the original schematic numbering for now) handles the control signals, U4 is D4-7 and U3 is D0-3. PORTC drives U5 and thus also handles all control signals.

We can also see that the data lines are now fully bidirectionally connected so that each can be connected to an OUTPUT or an INPUT depending on the state of the PC2 line. PORTB handles the OUTPUT and PORTA is the input.

The control signals are still mirrored as determined in the first part, but now we can see that some are OUTPUTs and some are INPUTs. The mappings from PC0-7 through to the link pins is shown below (note I’ve reverted to using the same PDS connector pin numbers as the ZX Spectrum schematic in the diagram above and table below).

There are two swapped pairs of connections, two common, and one unique to each.

As mentioned previously, the ZX Spectrum interface does not connect to pins 9,11,13,15 so that implies to me that it would not work out of link 2 without remapping in the software for the alternative pinout.

From working through the ZX Spectrum monitor code in part 1, we can infer the following functions:

• Pin 3 (OUT): PC to Target CLOCK
• Pin 5 (IN): Target to PC CLOCK/ACK

We can also note the following:

• Pin 11 (OUT): Direction based on PC2. HIGH = PC to Target; LOW = Target to PC

From this point I can now fully recreate the schematic and start to think about recreating the PCB.

The PC Hardware

One slight sticking point in remaking the PCB was getting useful dimensions for an XT era ISA card. Two useful references I found were:

• The ISA Spec can be found as part of the PC XT Technical Reference: https://bitsavers.org/pdf/ibm/pc/xt/6361459_PC_XT_Technical_Reference_Apr84.pdf
• Researched 8-bit ISA card dimensions: https://www.andavno.com/?p=87

The actual spec wasn’t massively useful to me. I don’t know if the ends of cards was slightly different in PC XT systems, but it doesn’t seem to match the photos of the PDS PC card. The second link was very well researched and complete however, so I went with that.

One compromise though was trying to keep the card within a 100x100mm footprint, so I’ve not extended completely to what I believe will be long enough to have an end plate.

The Schematic

The updated schematic is shown above. I’ve added a few things I’d expect to see on a modern design – additional 100nF capacitors (one for each IC), and a resistor network to pull up all unused inputs to the 74LS04.

I originally went with the ZX Spectrum version of the 16-way connector, but then when it came to assigning footprints, to get a right-angled IDC connector meant pin one was now in the wrong place, so I had to revert to the alternative pin numbering as per the original schematic.

The PCB

I’ve followed the original layout used on the PC card remake as far as possible, reasoning that the person who did this almost certainly knows a lot more about electronics than I do.

One thing I wasn’t sure about was a GND fill. I initially created a fill zone, but then decided I’d follow the original lead and use explicit GND connections. If someone advises that a fill will be better then it is pretty trivial to add in.

Other points to note:

• A already mentioned I’ve kept this within the 100x100mm footprint. This leaves two unknowns: will it be tall enough to be useful; and will it extend to the edge of a PC case?
• The two connectors extend beyond the edge of the PCB, so they hopefully will be available at the edge of a PC.
• The dimensions are such that more of the PCB is off to the right compared to the photos of the remade board I’ve seen.
• I’ve not been able to include mounting holes in any useful position whilst retaining the 100x100mm footprint.

This will do for now, but I think it is highly likely there will need to be some physical adjustments for this to be usable.

Conclusion

I believe I’ve got an accurate schematic for the board based on the photos available and I now have design for a candidate PCB. The problem is that I don’t know anything about what the software is expecting when it drives the Intel 8255 to work the PDS interface.

There is also the small matter of needing an ISA bus in a PC…

I’m hoping to get these boards published somewhere but right now, I’m not clear what the licensing issues would be. These boards are not available anymore, but at some point this was a company’s IPR.

For now, I’ll keep blogging observations and see what the interest is.

Next up will be some remake of the target PCBs.

Kevin

PDS – the Programmers Development System – Part 2

This series of posts looks at the Programmers Development System (PDS).

• Part 1 – Introduction, background and some initial reverse engineering.
• Part 2 – A closer look at the PC ISA Interface card.

Having now got a bit of an idea of how the PDS appears to work in my previous post (PDS – the Programmers Development System) I’m now taking another look at the PC interface and starting to think about the possibility of recreating the system.

The PC Interface

Having decided I couldn’t rely on the schematic on the CPC wiki, I’ve taken the printout-versions of the PCB traces and started tracing them through to see what is really going on. It was greatly helped by the PCB view that can be found here: https://lemmings.info/pds-programmers-development-system/

Of course, I am assuming here that the remade PC card does actually work.

It turns out the ISA to Intel 8255 part was fine, including the address decoding, but the three 8255 IO ports, through the octal line buffers, to the two PDS links are fundamentally missing some key links.

Essentially the three 74LS244s are configured for half in A->Y form and half in Y->A. The three IO ports (PORT A, B, C) are also split in half. This means that most of this circuit is working in 4-bit chunks.

The high level linkages are shown below.

So here we can see how the A halves of each of the 244s handles OUTPUT and the B halves handle INPUT. We can also see that U5 (sticking with the original schematic numbering for now) handles the control signals, U4 is D4-7 and U3 is D0-3. PORTC drives U5 and thus also handles all control signals.

We can also see that the data lines are now fully bidirectionally connected so that each can be connected to an OUTPUT or an INPUT depending on the state of the PC2 line. PORTB handles the OUTPUT and PORTA is the input.

The control signals are still mirrored as determined in the first part, but now we can see that some are OUTPUTs and some are INPUTs. The mappings from PC0-7 through to the link pins is shown below (note I’ve reverted to using the same PDS connector pin numbers as the ZX Spectrum schematic in the diagram above and table below).

There are two swapped pairs of connections, two common, and one unique to each.

As mentioned previously, the ZX Spectrum interface does not connect to pins 9,11,13,15 so that implies to me that it would not work out of link 2 without remapping in the software for the alternative pinout.

From working through the ZX Spectrum monitor code in part 1, we can infer the following functions:

• Pin 3 (OUT): PC to Target CLOCK
• Pin 5 (IN): Target to PC CLOCK/ACK

We can also note the following:

• Pin 11 (OUT): Direction based on PC2. HIGH = PC to Target; LOW = Target to PC

From this point I can now fully recreate the schematic and start to think about recreating the PCB.

The PC Hardware

One slight sticking point in remaking the PCB was getting useful dimensions for an XT era ISA card. Two useful references I found were:

• The ISA Spec can be found as part of the PC XT Technical Reference: https://bitsavers.org/pdf/ibm/pc/xt/6361459_PC_XT_Technical_Reference_Apr84.pdf
• Researched 8-bit ISA card dimensions: https://www.andavno.com/?p=87

The actual spec wasn’t massively useful to me. I don’t know if the ends of cards was slightly different in PC XT systems, but it doesn’t seem to match the photos of the PDS PC card. The second link was very well researched and complete however, so I went with that.

One compromise though was trying to keep the card within a 100x100mm footprint, so I’ve not extended completely to what I believe will be long enough to have an end plate.

The Schematic

The updated schematic is shown above. I’ve added a few things I’d expect to see on a modern design – additional 100nF capacitors (one for each IC), and a resistor network to pull up all unused inputs to the 74LS04.

I originally went with the ZX Spectrum version of the 16-way connector, but then when it came to assigning footprints, to get a right-angled IDC connector meant pin one was now in the wrong place, so I had to revert to the alternative pin numbering as per the original schematic.

The PCB

I’ve followed the original layout used on the PC card remake as far as possible, reasoning that the person who did this almost certainly knows a lot more about electronics than I do.

One thing I wasn’t sure about was a GND fill. I initially created a fill zone, but then decided I’d follow the original lead and use explicit GND connections. If someone advises that a fill will be better then it is pretty trivial to add in.

Other points to note:

• A already mentioned I’ve kept this within the 100x100mm footprint. This leaves two unknowns: will it be tall enough to be useful; and will it extend to the edge of a PC case?
• The two connectors extend beyond the edge of the PCB, so they hopefully will be available at the edge of a PC.
• The dimensions are such that more of the PCB is off to the right compared to the photos of the remade board I’ve seen.

This will do for now, but I think it is highly likely there will need to be some physical adjustments for this to be usable.

Conclusion

I believe I’ve got an accurate schematic for the board based on the photos available and I now have design for a candidate PCB. The problem is that I don’t know anything about what the software is expecting when it drives the Intel 8255 to work the PDS interface.

There is also the small matter of needing an ISA bus in a PC…

I’m hoping to get these boards published somewhere but right now, I’m not clear what the licensing issues would be. These boards are not available anymore, but at some point this was a company’s IPR.

For now, I’ll keep blogging observations and see what the interest is.

Next up will be some remake of the target PCBs.

Kevin

PDS – the Programmers Development System – Part 2

This series of posts looks at the Programmers Development System (PDS).

• Part 1 – Introduction, background and some initial reverse engineering.
• Part 2 – A closer look at the PC ISA Interface card.
• Part 3 – Remaking the target interfaces.

Having now got a bit of an idea of how the PDS appears to work in my previous post (PDS – the Programmers Development System) I’m now taking another look at the PC interface and starting to think about the possibility of recreating the system.

The PC Interface

Having decided I couldn’t rely on the schematic on the CPC wiki, I’ve taken the printout-versions of the PCB traces and started tracing them through to see what is really going on. It was greatly helped by the PCB view that can be found here: https://lemmings.info/pds-programmers-development-system/

Of course, I am assuming here that the remade PC card does actually work.

It turns out the ISA to Intel 8255 part was fine, including the address decoding, but the three 8255 IO ports, through the octal line buffers, to the two PDS links are fundamentally missing some key links.

Essentially the three 74LS244s are configured for half in A->Y form and half in Y->A. The three IO ports (PORT A, B, C) are also split in half. This means that most of this circuit is working in 4-bit chunks.

The high level linkages are shown below.

So here we can see how the A halves of each of the 244s handles OUTPUT and the B halves handle INPUT. We can also see that U5 (sticking with the original schematic numbering for now) handles the control signals, U4 is D4-7 and U3 is D0-3. PORTC drives U5 and thus also handles all control signals.

We can also see that the data lines are now fully bidirectionally connected so that each can be connected to an OUTPUT or an INPUT depending on the state of the PC2 line. PORTB handles the OUTPUT and PORTA is the input.

The control signals are still mirrored as determined in the first part, but now we can see that some are OUTPUTs and some are INPUTs. The mappings from PC0-7 through to the link pins is shown below (note I’ve reverted to using the same PDS connector pin numbers as the ZX Spectrum schematic in the diagram above and table below).

There are two swapped pairs of connections, two common, and one unique to each.

As mentioned previously, the ZX Spectrum interface does not connect to pins 9,11,13,15 so that implies to me that it would not work out of link 2 without remapping in the software for the alternative pinout.

From working through the ZX Spectrum monitor code in part 1, we can infer the following functions:

• Pin 3 (OUT): PC to Target CLOCK
• Pin 5 (IN): Target to PC CLOCK/ACK

We can also note the following:

• Pin 11 (OUT): Direction based on PC2. HIGH = PC to Target; LOW = Target to PC

From this point I can now fully recreate the schematic and start to think about recreating the PCB.

The PC Hardware

One slight sticking point in remaking the PCB was getting useful dimensions for an XT era ISA card. Two useful references I found were:

• The ISA Spec can be found as part of the PC XT Technical Reference: https://bitsavers.org/pdf/ibm/pc/xt/6361459_PC_XT_Technical_Reference_Apr84.pdf
• Researched 8-bit ISA card dimensions: https://www.andavno.com/?p=87

The actual spec wasn’t massively useful to me. I don’t know if the ends of cards was slightly different in PC XT systems, but it doesn’t seem to match the photos of the PDS PC card. The second link was very well researched and complete however, so I went with that.

One compromise though was trying to keep the card within a 100x100mm footprint, so I’ve not extended completely to what I believe will be long enough to have an end plate.

The Schematic

The updated schematic is shown above. I’ve added a few things I’d expect to see on a modern design – additional 100nF capacitors (one for each IC), and a resistor network to pull up all unused inputs to the 74LS04.

I originally went with the ZX Spectrum version of the 16-way connector, but then when it came to assigning footprints, to get a right-angled IDC connector meant pin one was now in the wrong place, so I had to revert to the alternative pin numbering as per the original schematic.

The PCB

I’ve followed the original layout used on the PC card remake as far as possible, reasoning that the person who did this almost certainly knows a lot more about electronics than I do.

I’ve also tried to keep the connectors as close to the positions on the original as far as possible, whilst still keeping within the 100x100mm PCB total size.

One thing I wasn’t sure about was a GND fill. I initially created a fill zone, but then decided I’d follow the original lead and use explicit GND connections. If someone advises that a fill will be better then it is pretty trivial to add in.

Other points to note:

• A already mentioned I’ve kept this within the 100x100mm footprint. This leaves two unknowns: will it be tall enough to be useful; and will it extend to the edge of a PC case?
• The two connectors are roughly in the same horizontal position as the original card. They seem comparable to where the pins align with the edge connector anyway. An earlier iteration had them extending beyond the PCB, but I’ve redesigned it to mirror the original card.
• The dimensions are such that more of the PCB is off to the right compared to the photos of the original or the remade board I’ve seen.
• I’ve not been able to include mounting holes in any useful position whilst retaining the 100x100mm footprint.

The current dimensions of the above PCB are shown below.

This will do for now, but I think it is highly likely there will need to be some more physical adjustments at some point for this to be usable.

Conclusion

I believe I’ve got an accurate schematic for the board based on the photos available and I now have design for a candidate PCB. The problem is that I don’t know anything about what the software is expecting when it drives the Intel 8255 to work the PDS interface.

There is also the small matter of needing an ISA bus in a PC…

I’m hoping to get these boards published somewhere but right now, I’m not clear what the licensing issues would be. These boards are not available anymore, but at some point this was a company’s IPR.

For now, I’ll keep blogging observations and see what the interest is.

Next up will be some remake of the target PCBs.

Kevin

https://www.europesays.com/fi/240482/ Lilia Leppilampi on Emilia Vuorisalmen ja Mikko Leppilammen tytär. Lilia loistaa tanssijana ja somevaikuttajana – katso upeat kuvat ja millaista somesisältöä hän teke #äiti #äitiJaTytär #Celebrities #EmiliaVuorisalmi #Entertainment #FI #Finland #Finnish #isä #IsäJaTytär #IsäTytärSuhde #Julkkikset #kaunotar #kuvat #lifestyle #LiliaLeppilampi #MikkoLeppilampi #somekaunotar #somekuva #somekuvat #somevaikuttaja #Suomi #tanssija #tytär #viihde

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https://www.europesays.com/fi/235186/ Janne Virtanen kertoo Apu-lehden haastattelussa leskenelämästään ja tyttärensä Vienon tulevaisuudesta – tottunut jo olemaan itsekseen #äiti #ApuLehti #Celebrities #Entertainment #FI #Finland #Finnish #HannaRiikkaSiitonen #isä #IsäTytärSuhde #JanneVirtanen #Julkkikset #Kuolema #kuolemanpelko #kuollut #leskeys #leski #Perhe #seurustelu #Suomi #syöpä #syöpäkuolema #tytär #vaimo #vieno #VienoVirtanen #viihde #yksinäisyys

https://www.europesays.com/fi/233502/ Osmo Ikonen paljastaa, miten musiikkiura pahentaa vauvaikävää, ja miltä pikkuvauvan isän keikkareitit voivat näyttää. Mukana harvinainen vauvanheittelyvideo #bändi #Celebrities #Entertainment #erikoisjoukot #FI #Finland #Finnish #isä #IsäPoikaSuhde #Julkkikset #lapsiperhe #LapsiperheenArki #laulaja #LaulajaLauluntekijä #Musiikki #Muusikko #OsmoIkonen #Perhe #perhearki #poika #SunriseAvenue #Suomi #TheVoiceOfFinland #vauva #VauvaArki #viihde

https://www.europesays.com/fi/232413/ Minna Kauppi: Maailmanmestarisuunnistajasta innokas lätkämutsi #äiti #Asikkala #avoliitto #avomies #avopari #avopuoliso #avovaimo #Entertainment #esikoinen #FI #Finland #Finnish #isä #Jääkiekko #juniorikiekko #juniorilätkä #juniorit #Lapset #lapsi #lapsiperhe #LapsiperheenArki #mies #MinnaKauppi #Pelicans #Perhe #perhearki #poika #puoliso #SipeSantapukki #Suomi #urheilulaji #vaimo #viihde

1993, France 🇫🇷
CELOGIC développe un "PC chantier" :
PC transportable durci industriel
Une autre époque du hardware, plus proche de l’instrumentation que du computing grand public.

As-tu connu cette french tech massive ?

#RetroComputing #IndustrialPC #ISA #MadeInFrance #Telecom #HardwareHistory

1993, France 🇫🇷
CELOGIC développe un "PC chantier" :
PC transportable durci industriel
Une autre époque du hardware, plus proche de l’instrumentation que du computing grand public.

As-tu connu cette french tech massive ?

#RetroComputing #IndustrialPC #ISA #MadeInFrance #Telecom #HardwareHistory

1993, France 🇫🇷
CELOGIC développe un "PC chantier" :
PC transportable durci industriel
Une autre époque du hardware, plus proche de l’instrumentation que du computing grand public.

As-tu connu cette french tech massive ?

#RetroComputing #IndustrialPC #ISA #MadeInFrance #Telecom #HardwareHistory

1993, France 🇫🇷
CELOGIC développe un "PC chantier" :
PC transportable durci industriel
Une autre époque du hardware, plus proche de l’instrumentation que du computing grand public.

As-tu connu cette french tech massive ?

#RetroComputing #IndustrialPC #ISA #MadeInFrance #Telecom #HardwareHistory

1993, France 🇫🇷
CELOGIC développe un "PC chantier" :
PC transportable durci industriel
Une autre époque du hardware, plus proche de l’instrumentation que du computing grand public.

As-tu connu cette french tech massive ?

#RetroComputing #IndustrialPC #ISA #MadeInFrance #Telecom #HardwareHistory

https://www.europesays.com/fi/226854/ Niina Lahtinen paljastaa podcastissa syömishäiriönsä taustat #Entertainment #FI #Finland #Finnish #isä #JokoSaaLuovuttaa? #kimmo #laihdutus #laihdutuskuuri #lapsuus #NiinaLahtinen #paljastus #PaulaNoronen #podcast #Suomi #Terveys #ura #viihde

https://www.europesays.com/es/509227/ ‘MasterChef 14’ expulsó a uno de los más queridos por «maltratar los productos» delante de Isa Pantoja y Asraf #14 #asraf #delante #Entertainment #Entretenimiento #ES #España #expulso #isa #maltratar #masterchef #pantoja #productos #queridos #Spain #TV

https://www.europesays.com/at/111708/ Salzburg blüht auf – „Ich fühle mich hier fast wie in Japan!“ #AT #Austria #ISA #Japan #Österreich #Salzburg #Stadler #Wien

https://www.europesays.com/fi/224477/ Niko Nousiainen paljastaa: Tällainen isä haluan olla #Celebrities #elämänmuutos #Entertainment #FI #Finland #Finnish #isä #isyys #Julkkikset #lapsi #NikoNousiainen #Perhe #rakkaus #Suomi #vauva #VauvaArki #viihde

Traders placed over $1bn in perfectly timed bets on the Iran war

Suspicious wagers on the US-Israel war in Iran are creating huge windfalls and raising concerns among lawmakers

https://www.theguardian.com/world/2026/apr/18/iran-war-bets-ethics-concerns

#Iran #ISA #Israel #war #betting #gambling #dystopia #corruption #PolyMarket

https://www.europesays.com/fi/223045/ Olli Hermanilta perhepaljastus | Seiska #Celebrities #Entertainment #FI #Finland #Finnish #isä #isyys #Julkkikset #Lapset #Musiikki #OlliHerman #Perhe #popeda #RadioRock #radiogaala #rakkaus #RecklessLove #rock #Suomi #viihde

Viele 🚗 🚚 🚗 treffen sich gerade auf der A3: Nürnberg -> Passau, zwischen 3.0 km hinter Spitzig Berg und 3.6 km vor Kühberg und blockieren die #Autobahn.

Es könnte sein, dass sie heute die #EU-weit verpflichtende Installation eines intelligenten, übersteuerbaren Geschwindigkeitsassistenten in alle #Neufahrzeuge fordern. Das könnte langfristig die Zahl der #Verkehrstote​n um 20% reduzieren. Viel weniger Autos hätten #Totalschaden. 🚗⚠️ #Verkehrssicherheit #ISA (Quelle: ETSC)

@IngridHbn ik mag toch hopen dat deze organisatie ook een dag van de lage motorkap, van de lichte auto, van de auto zonder videoscherm, met automatische niet omgaanbare snelheidsbeperking instelt?
Het is bijvoorbeeld toch niet ongemerkt voorbij gegaan dat de USA aan Europa monstertrucks probeert op te dringen? Je weet wel, laaghangend fruit, oorzaken aanpakken ipv dweilen met de kraan open. #ISA #SUV

883,000 Brits with £3,500 or more in savings to receive imminent HMRC tax bill

https://fed.brid.gy/r/https://metro.co.uk/2026/04/07/883-000-brits-3-500-savings-receive-imminent-hmrc-tax-bill-27884187/

https://www.europesays.com/fi/?p=214215 Kruununprinsessa Mette-Maritin Marius-poika vankilassa: Isä kurvasi paikalle ökyautolla #auto #BreakingNews #BreakingNews #FeaturedNews #FeaturedNews #FI #Finland #Finnish #Headlines #isä #KruununprinssiHaakon #LatestNews #LatestNews #MainNews #MainNews #MariusBorgHøiby #MetteMarit #MortenBorg #News #NorjanHovi #oikeudenkäynti #Otsikot #Pääuutiset #Rikos #Suomi #syytteet #tesla #TopStories #TopStories #Ulkomaat #Uutiset #vankila #World #WorldNews #WorldNews

Mistähän tulee sanonta, että joku asia ”tekee eetvarttia”? Kuka se Edward / Edvard on? Mutta #isä sanoi joskus niin. Nyt tekee eetvarttia olla lomalla. #fensterfreitag

Savvy UK savers can make 1 change to avoid £3,775 mistake – Daily Express

Savvy UK savers can make 1 change to avoid £3,775 mistake  Daily ExpressWhich is the best low-cost stocks and…
#NewsBeep #News #US #USA #UnitedStates #UnitedStatesOfAmerica #Personalfinance #Business #interactiveinvestor #interactiveinvestorISA #interactiveinvestorlatest #interactiveinvestornews #interactiveinvestorupdate #Investing #ISA #PersonalFinance #Savings
https://www.newsbeep.com/us/552961/

Savvy UK savers can make 1 change to avoid £3,775 mistake – Daily Express

Savvy UK savers can make 1 change to avoid £3,775 mistake  Daily ExpressWhich is the best low-cost stocks and…
#NewsBeep #News #US #USA #UnitedStates #UnitedStatesOfAmerica #Personalfinance #Business #interactiveinvestor #interactiveinvestorISA #interactiveinvestorlatest #interactiveinvestornews #interactiveinvestorupdate #Investing #ISA #PersonalFinance #Savings
https://www.newsbeep.com/us/552961/

Savvy UK savers can make 1 change to avoid £3,775 mistake – Daily Express

Savvy UK savers can make 1 change to avoid £3,775 mistake  Daily ExpressThis easy switch could boost your Isa…
#NewsBeep #News #Personalfinance #Business #Finance #interactiveinvestor #interactiveinvestorISA #interactiveinvestorlatest #interactiveinvestornews #interactiveinvestorupdate #Investing #ISA #PersonalFinance #Savings #UK #UnitedKingdom
https://www.newsbeep.com/uk/502035/

https://www.europesays.com/uk/858555/ Savvy UK savers can make 1 change to avoid £3,775 mistake – express.co.uk #Business #Finance #InteractiveInvestor #InteractiveInvestorISA #InteractiveInvestorLatest #InteractiveInvestorNews #InteractiveInvestorUpdate #Investing #ISA #PersonalFinance #Savings #UK #UnitedKingdom

Muslims should follow Jesus, as the Quran clearly states that those who follow Jesus shall be superior to those who do not believe!

http://john1126.com/721

#Muslims #Jesus #Isa #Quran #Islam #Koran

And in the second mystery AT box I find this!

#isa #retropc #oddhardware #singular #intel8255 #nec8255