Reflowing the solder made no difference so I pulled the SRAM daughter board and soldered an SRAM chip (plus the required capacitor) onto the board and it worked first time.
It looks like PCBWay either fitted a faulty chip or it was damaged by the soldering process. *sigh*
New project: An ACT Apricot F1 "barn find"
- stephen_usher
- Posts: 5582
- Joined: Mon Nov 13, 2017 7:19 pm
- Location: Oxford, UK.
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Re: New project: An ACT Apricot F1 "barn find"
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
- stephen_usher
- Posts: 5582
- Joined: Mon Nov 13, 2017 7:19 pm
- Location: Oxford, UK.
- Contact:
Re: New project: An ACT Apricot F1 "barn find"
Note: NO BODGE WIRES!!!!!!!
HOW IS THIS POSSIBLE?!
Hehe
HOW IS THIS POSSIBLE?!
Hehe
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
- stephen_usher
- Posts: 5582
- Joined: Mon Nov 13, 2017 7:19 pm
- Location: Oxford, UK.
- Contact:
Re: New project: An ACT Apricot F1 "barn find"
It's been running GEM for two hours now without issue. Looks like it may be working OK.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
Re: New project: An ACT Apricot F1 "barn find"
stephen_usher wrote: ↑Sun Sep 26, 2021 3:04 pm Note: NO BODGE WIRES!!!!!!!
HOW IS THIS POSSIBLE?!
Hehe
- stephen_usher
- Posts: 5582
- Joined: Mon Nov 13, 2017 7:19 pm
- Location: Oxford, UK.
- Contact:
Re: New project: An ACT Apricot F1 "barn find"
Tonight I thought I'd had a cunning plan to stop the external floppy drive running all the time and have it only run when the disk was accessed (as the MOTOR-ON signal is always asserted), I'd use the HEAD-LOAD signal, as that should be asserted when data is required and "modern" drives spin up quickly enough.
I was thwarted, however. I didn't notice that it only asserted the HDLD signal when drive A was accessed. Bother!
I was thwarted, however. I didn't notice that it only asserted the HDLD signal when drive A was accessed. Bother!
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
- stephen_usher
- Posts: 5582
- Joined: Mon Nov 13, 2017 7:19 pm
- Location: Oxford, UK.
- Contact:
Re: New project: An ACT Apricot F1 "barn find"
I'm slowly getting back into designing the hard disk interface emulation again.
I purchased a number of CD4020BE chips as they were advertised as 14 stage ripple counter chips and I need 13 bits of address to sequentially access 8K of SRAM. It wasn't until I started doing a schematic that I discovered that bits 2 and 3 actually don't come out on pins on the chip, only 1,4-14, so they're useless.
Instead I'm going to have to build something out of a 12 bit counter, the CD4040BE and a 74LS112 dual flip-flop (negative edge triggered). Those should be arriving today and I can prototype a circuit on a breadboard over the weekend. I've just got to work out a quick and dirty way of driving LEDs from the outputs so I can see that it's counting correctly. I can then use the signal generator on the new hand-held oscilloscope to clock the counter. I can use the top bit of the counter as an input to the first flip-flop, and the output of that into the second one. The output of this flip-flop can be inverted and passed into the reset, so both chips get reset when the top bit gets set.
I purchased a number of CD4020BE chips as they were advertised as 14 stage ripple counter chips and I need 13 bits of address to sequentially access 8K of SRAM. It wasn't until I started doing a schematic that I discovered that bits 2 and 3 actually don't come out on pins on the chip, only 1,4-14, so they're useless.
Instead I'm going to have to build something out of a 12 bit counter, the CD4040BE and a 74LS112 dual flip-flop (negative edge triggered). Those should be arriving today and I can prototype a circuit on a breadboard over the weekend. I've just got to work out a quick and dirty way of driving LEDs from the outputs so I can see that it's counting correctly. I can then use the signal generator on the new hand-held oscilloscope to clock the counter. I can use the top bit of the counter as an input to the first flip-flop, and the output of that into the second one. The output of this flip-flop can be inverted and passed into the reset, so both chips get reset when the top bit gets set.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
- stephen_usher
- Posts: 5582
- Joined: Mon Nov 13, 2017 7:19 pm
- Location: Oxford, UK.
- Contact:
Re: New project: An ACT Apricot F1 "barn find"
Could someone advise me if for a temporary test just sticking an LED + 220 ohm resistor onto a TTL chip pin would work?
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.