Search found 90 matches

by ijor
Fri Dec 21, 2018 8:51 pm
Forum: HARDWARE DISCUSSIONS
Topic: BLITTER RE-CREATION THOUGHTS
Replies: 285
Views: 36343

Re: BLITTER RE-CREATION THOUGHTS

I connected up the IDT buffer again for a final test... That one only seems to work with a 2.2K pulldown on the 3.3V side.. When either side goes low, the other side goes low , so it does actually work.. sort of... I only get 3.3V on the 5V side..Which is kind of expected anyway. But what worries m...
by ijor
Fri Dec 21, 2018 2:17 am
Forum: HARDWARE DISCUSSIONS
Topic: BLITTER RE-CREATION THOUGHTS
Replies: 285
Views: 36343

Re: BLITTER RE-CREATION THOUGHTS

The chip which isn't mosfet based is the 74LCX245-D, which of course needs direction control. It was that chip I am considering using with Ijors patched blitter code. If you decide to use the patched core remember that a solution for the open drain signals is still pending. I didn't do anything wit...
by ijor
Wed Dec 19, 2018 11:56 am
Forum: MONGREL EDITION DEVELOPMENT & INFO
Topic: DMA HEADER REV H1
Replies: 27
Views: 4369

Re: DMA HEADER REV H1

I wonder what the internal connector on the Mega was designed for when the external DMA only has 19 pins? Probably the same reason that the floppy cable has 34 wires but only use half of them. To reduce crosstalk between the signals. If you check the pinout you would see that the extra gnd wires ar...
by ijor
Wed Dec 19, 2018 11:16 am
Forum: MONGREL EDITION DEVELOPMENT & INFO
Topic: DMA HEADER REV H1
Replies: 27
Views: 4369

Re: DMA HEADER REV H1

Whilst I do not have an UltraSatan(US) (a friend has one), the schematics show that it also has a 20 pin IDC connector and a micro USB for power. From what I have and the schematic on the US, all have the same 20 pin IDC connector. Not sure if that was an answer to my post or not. But yes, all have...
by ijor
Wed Dec 19, 2018 11:09 am
Forum: MONGREL EDITION DEVELOPMENT & INFO
Topic: DMA HEADER REV H1
Replies: 27
Views: 4369

Re: DMA HEADER REV H1

I don't even know of any boards which even use the connector. Other than ultrasatan, but thats likely going to be a cable. I'm assuming US uses the same pinout, Jookie never got back to me with the pinout :( US schematics and Eagle files are available at Jookie's site: http://joo.kie.sk/wp-content/...
by ijor
Tue Dec 18, 2018 2:14 pm
Forum: HARDWARE DISCUSSIONS
Topic: BLITTER RE-CREATION THOUGHTS
Replies: 285
Views: 36343

Re: BLITTER RE-CREATION THOUGHTS

I don't think that would work. You could use an open collector buffer for BR because it is an output only pin. But DTACK is bidirectional. Ah yes you are right there. I was only thinking blitter side. There is another possible solution for these open drain signals without using any bidirectional ch...
by ijor
Tue Dec 18, 2018 12:15 pm
Forum: HARDWARE DISCUSSIONS
Topic: BLITTER RE-CREATION THOUGHTS
Replies: 285
Views: 36343

Re: BLITTER RE-CREATION THOUGHTS

For things like DTACK, I may use a single open collector buffer.. they normally good for 30V pull down voltages. So that would solve that problem without needing anything "fancy" doing. I don't think that would work. You could use an open collector buffer for BR because it is an output only pin. Bu...
by ijor
Mon Dec 17, 2018 1:38 pm
Forum: HARDWARE DISCUSSIONS
Topic: BLITTER RE-CREATION THOUGHTS
Replies: 285
Views: 36343

Re: BLITTER RE-CREATION THOUGHTS

Attached is a modified Suska top VHDL file to work with bidirectional buffers. There are three direction control signals. One for the data bus, other for the address bus, and a third one for the bus control signals. Currently the polarity is such that a high level indicates that the FPGA is driving ...
by ijor
Tue Dec 11, 2018 4:31 pm
Forum: ELECTRONICS
Topic: Microscopic chip analysis
Replies: 8
Views: 1185

Re: Microscopic chip analysis

I reverse engineered the whole ST chipset and several other chips including the 68000. So is there proper logic diagrams of the GLUE, MMU etc then ? I didn't release full schematics yet. You said that "nothing has been (fully) reversed engineered in the ST chipset", and that is not true. You don't ...
by ijor
Tue Dec 11, 2018 1:10 pm
Forum: ELECTRONICS
Topic: Microscopic chip analysis
Replies: 8
Views: 1185

Re: Microscopic chip analysis

Decapping and reverse engineering old school chips is my favorite hobby :) One interesting place to visit is visual 6502. If smaller fpgas become available, drop-in replacements of the chips might even be possible but I guess it will always be more expansive than a single fpga that emulates all of t...

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