Search found 1300 matches
- Thu Jan 25, 2024 3:18 pm
- Forum: Hardware
- Topic: Minerva Mk2 Remake
- Replies: 41
- Views: 2567
Re: Minerva Mk2 Remake
The original board was a little larger than the ROM socket footprint - having the RTC chip and GAL to accommodate. A straight copy would at least resurrect the I2C portion of Minerva. If the components were SMD - they should all fit into the same space, with the option of additional ROM images / I2C...
- Tue Jan 23, 2024 10:24 pm
- Forum: Hardware
- Topic: Minerva Mk2 Remake
- Replies: 41
- Views: 2567
Re: Minerva Mk2 Remake
The main reason would be to isolate the I2C SCL and SDA pins if these are taken out to the outside world - giving protection against mishaps.
- Tue Jan 23, 2024 2:36 pm
- Forum: Hardware
- Topic: Minerva Mk2 Remake
- Replies: 41
- Views: 2567
Re: Minerva Mk2 Remake
Is this to include the I2C components (clock and I2C output) ? If so could I suggest an I2C buffer chip be added ?
- Tue Jan 23, 2024 10:21 am
- Forum: Compatibles Corner
- Topic: ICL OPD 3 vertical white stripes fault
- Replies: 24
- Views: 1322
Re: ICL OPD 3 vertical white stripes fault
The SRAM chip does not need or use any signals from the 2 Sinclair ULA chips ZX8301/ZX8302 - it gets it's select signal from the ICL ULA, but this is gated with FC2 (high in supervisor mode) so that the RAM can only be accessed when Selected by address decoded by the ICL ULA and FC2 indicating Super...
- Mon Jan 22, 2024 10:31 pm
- Forum: Compatibles Corner
- Topic: ICL OPD 3 vertical white stripes fault
- Replies: 24
- Views: 1322
Re: ICL OPD 3 vertical white stripes fault
The other one comes from the NAND gate - with FC2 and the CMOS RAM enable from the ICL ULA as the inputs to the gate - so the RAM can only be accessed in supervisor mode.
- Mon Jan 22, 2024 10:19 pm
- Forum: Compatibles Corner
- Topic: ICL OPD 3 vertical white stripes fault
- Replies: 24
- Views: 1322
Re: ICL OPD 3 vertical white stripes fault
I think that comes from the drain of FT5 - controlled by the powerdown on the 15 way connector, that FET will ground the /CE input when powerdown is at 5v (this signal goes to multiple places) - the drain has a load resistor connected to the diode junction from 3v lithium, and diode from 5v, so eith...
- Mon Jan 22, 2024 6:08 pm
- Forum: Compatibles Corner
- Topic: ICL OPD 3 vertical white stripes fault
- Replies: 24
- Views: 1322
Re: ICL OPD 3 vertical white stripes fault
The ROMS are I think in 3 parts - the first 64K are a combined OS ROM - so that's ROM A and B ROM C has a header like other application ROM's - so I wonder if this OS Extension is handled as an application ROM - ROM D seems to be the one that may have different code in it and seems to be mostly prov...
- Sun Jan 21, 2024 1:44 pm
- Forum: Compatibles Corner
- Topic: ICL OPD 3 vertical white stripes fault
- Replies: 24
- Views: 1322
Re: ICL OPD 3 vertical white stripes fault
Seems odd you get a ROM fault when it had worked before you put it into storage. I noticed that on both my daughter boards - 3 of the ROM chips are mask ROM's and the last one closest to the processor - the one that's in position '7' of the LS137 decode at address 0xA8000 - is an EPROM. It would be ...
- Sat Jan 20, 2024 10:04 pm
- Forum: Compatibles Corner
- Topic: ICL OPD 3 vertical white stripes fault
- Replies: 24
- Views: 1322
Re: ICL OPD 3 vertical white stripes fault
I'm wondering if this is a fault with ZX8302 (9v battery) power circuit?
- Fri Jan 19, 2024 10:10 am
- Forum: Compatibles Corner
- Topic: ICL OPD
- Replies: 180
- Views: 167755
Re: ICL OPD
On the WD1770/WD1772 question - https://www.bing.com/ck/a?!&&p=a82800f7a09cfd2aJmltdHM9MTcwNTYyMjQwMCZpZ3VpZD0zNWNkMTA1ZS1hMmVmLTY3N2ItMTZhNC0wMzZjYTNkNzY2OTUmaW5zaWQ9NTQ5Mg&ptn=3&ver=2&hsh=3&fclid=35cd105e-a2ef-677b-16a4-036ca3d76695&psq=WD1770+WD1772+differences&u=a...