Re: MSX2 Compatible Computer Project [message #5630 is a reply to message #5451] |
Wed, 28 November 2018 17:56 |
Sergey
Messages: 236 Registered: October 2015 Location: Portland, OR
|
Senior Member |
|
|
Attached is the schematic for my variant of MSX2 compatible system.
It is based on lintweaker's work, on MSX datapack specs, as well as on multiple other sources.
A few notes:
- I plan to use a CPU supervisor circuit - ADM693/MAX693. This IC would generate proper reset signals and provide the battery power and chip select signals to the RTC (replacing a few transistors and several passive components)
- I tried to implement a flexible slot selection:
* The extended slot can be set to either slot 0 or slot 3
* The RAM can be either set to slot 3 or sub slot 2 (so it will be either slot 3, slot 0-2, or slot 3-2).
* The ROM is divided into four 64 KiB chunks, each one can be mapped to a different slot or sub slot. The intention is that the first chunk will be used for the Main MSX ROM, and the second for the Sub ROM, while 2 more are available for future extensions (e.g. Disk ROM). Now, I didn't do anything to prevent any part of the 64 KiB chunk to be mapped to the CPU. For example the 0x8000-0xFFFF area of the 64 KiB chunk containing Main ROM can be mapped, although it is not normally used by MSX. My assumption is that MSX BIOS and applications will not do that (and even if they do, it shouldn't be any harm... but please correct me if I am wrong).
- The default VDP for the system is v9938, but I've added a jumper that should make v9958 work as well. The video output is connected to an AD724 NTSC/PAL encoder with Composite and S-Video outputs. The encoder is set for NTSC timing (modern TVs are multi-system anyway, unless you're in US where they are NTSC). The RGB+Sync signals are available on the headers in case a different video output is desired. In my own opinion S-Video should provide a good enough quality, and if needed there are inexpensive S-Video to HDMI converters available. I'd appreciate though if someone will review the video output part of the schematic.
- I used a single supply op amp for the low pass filter for the PSG. Again, I'd appreciate if someone with analog electronics knowledge would check that part of the schematic
Thanks,
Sergey
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Re: MSX2 Compatible Computer Project [message #6525 is a reply to message #6523] |
Tue, 10 September 2019 09:36 |
jdgabbard
Messages: 76 Registered: March 2016
|
Member |
|
|
b1ackmai1er wrote on Tue, 10 September 2019 04:20Hi Doug,
Love the keyboard enclosure and the keycaps. Have you considered taking the enclosure up to the base of the keycaps?
How long does it make? Does it require a lot of "finishing"? Wondering how this would look in a hammertone paint finish.
Regards Phil.
Phil,
With this particular design it wasn't practical, since the case is the keyboard, the switches are hand wired. But on something like the omega, having a keyboard PCB allows for recessing the switches. And that is how I would design it.
Concerning fit and finish, it didn't require any more than any other painted project. Since the parts are 3D printed, it really comes down to the capabilities of your machine. But I heat welded the halves, filled and sanded, primed, then painted with a semi gloss enamel. The more you do the better it will look. Although I can't speculate on the hammertone, I'm not familiar with that finish.
Doug Gabbard
Creator of the G80-S Micro Computer and 'Porter' of TinyBASIC 2.5g
Website: http://retrodepot.net
z80 TinyBASIC 2.5g: http://retrodepot.net/?p=424
AtariAge Username: jdgabbard
|
|
|
|
|
|