OPL3 and 6502: am I being the weird one? - Page 1
Forum section: electronics / general

author: technix
author_rank: Super Contributor
timestamp: January 13, 2019, 08:03:34 pm
content: Am I the weird one if I designed a 6502-based machine with a YMF262/OPL3 audio chip? Also with the Propeller being unobtanium here in China what is the best option for a video solution?

author: Ian.M
author_rank: Super Contributor
timestamp: January 13, 2019, 08:54:53 pm
content: Probably, as I suspect you are entirely on your own for software support for it, but as its a lineal descendent of the original OPL synth, if it gives you that warm fuzzy feeling and desire to solder, go for it.As for graphics, if you don't want to go down the everything in a large FPGA road, consider hosting it on a Linux SoC board with HDMI out, emulating a graphics coprocessor of the era. That also gets you easy mass storage and keyboard + mouse support.

author: pamperchu
author_rank: Contributor
timestamp: January 14, 2019, 05:15:26 pm
content: I have thousands of NOS and recovered vintage ICs for that kind of thing. what parts are you looking for? for "video" you could use a CRT controller.

author: technix
author_rank: Super Contributor
timestamp: January 14, 2019, 06:29:33 pm
content: Quote from: pamperchu on January 14, 2019, 05:15:26 pmI have a MC68B45 CRT controller chip and 16kB dual port SRAM chip for a conflict-less DMA-less design if I want to. However I am not sure how should I hook up the 6845 though.

author: pamperchu
author_rank: Contributor
timestamp: January 15, 2019, 03:22:59 am
content: the 6845 i think as i read the datasheet, did not have a RAMDAC/ frame buffer and was only a raster crt driver. other chips would have made the "images" i guess. is that correct?you can make bitmaps on a eprom by hand for text or .. bitmaps, as a lookup table to feed into the 6845. the orignal fonts can be copied from old bios roms if you don't want to draw your own at first.it can get vastly more complex from there,I like the idea of using only vintage parts, ive designed/ not built, a "uv eprom solid state" digital music format using only early 80s chips @16bit/48khz..only part i haven't built

author: technix
author_rank: Super Contributor
timestamp: January 15, 2019, 03:53:53 am
content: Quote from: pamperchu on January 15, 2019, 03:22:59 amI am fully happy mixing the old and the new, so it doesn't bug me if I have to use for example a newer NOR parallel Flash chip for the character ROM. I would prefer a more integrated solution though. Is there any single-chip or similarly consolidated 8-bit ISA CGA or VGA chipset that has open documentations and reference schematics?

author: pamperchu
author_rank: Contributor
timestamp: January 15, 2019, 02:40:37 pm
content: i have a few in my hand right now and a bunch more if i looked for them,look up the HD63484 datasheetThe chip offered a high-level command which reduced software development costs. In this way, the ACRTC converted logical x – y coordinates to physical frame buffer addresses. It supported 38 commands, including LINE, RECTANGLE, POLYLINE, POLYGON, CIRCLE, ELLIPSE, ARC, ELLIPSE ARC, FILLED RECTANGLE, PAINT, PATTERN and COPY. An on-chip 32-byte pattern RAM could be used for powerful graphic environments. Conditional drawing functions were available for drawing patterns, color mixing, and software windowing, and it supported clipping and hitting.I have 2 sitting on my desk that are New old stock , there's about 100 chip tubes that i got from a surplus place 15 years ago and it looked like someone was building video computer systems of some type, all gold top ram chips of all sizes.I live right next to tektronix and a bunch of other IC fabs that made all this custom high end gear back then and common at the surplus store , what about using an old tektronix mainframe as the display, build the rest on the side as a plugin module?

author: technix
author_rank: Super Contributor
timestamp: January 15, 2019, 02:50:00 pm
content: Quote from: pamperchu on January 15, 2019, 02:40:37 pmFor the 65C02 I am thinking about using a 192px by 64px graphics LCD as its display output, and use a PIC16F1939 as the PS/2 keyboard processor. That board is more or less based on the WDC W65C02SXB design really.As of that type of CRTC I am more inclined to build it for my other vintage-style PC project, which is based on an NEC V40 and I wish it can run DOS as the finished product. That type of CRTC are more suited for a CGA or EGA compatible graphics controller. Also that specific chip is too big for my purpose here, as m DOS machine project is to be built as a stack of PC104 cards.

author: pamperchu
author_rank: Contributor
timestamp: January 15, 2019, 11:28:54 pm
content: most little LCD displays have built in controllers, its the simplest solution too. i was imagining like a small CRT being used

author: technix
author_rank: Super Contributor
timestamp: January 16, 2019, 03:36:51 pm
content: Quote from: pamperchu on January 15, 2019, 11:28:54 pmI don't even have a CRT, and for VGA outputs on my planned DOS machine I have to buy a LCD panel adapter kit and case to convert my spare 14-inch laptop LCD into a small VGA capable LCD monitor. (although I am keeping RGBI and raw OPL3 digital outputs in pin header form to allow the future addition of a HDMI adapter card.)

author: Ampera
author_rank: Super Contributor
timestamp: January 17, 2019, 01:30:26 am
content: Easiest solution for graphics I would be imagine what was said before, some Linux box to do all the frame buffery stuff.I think the big issue for anything else is how slow the 6502 is, and that goes with OPL3 chips. Even SID music on the C64 I wouldn't imagine to be all that much of a walk in the park for memory and computer time restrictions. No doubt that it's possible, and if you want to do it, go right ahead, who's gonna stop you?I've toyed around with the ideas of what would I put into my dream of an older machine, something I'd base around the 68k, and within that idea I've even thought of using processor driven video, with just simple circuitry for developing some sort of usable video output. Since 68k's are relatively cheap, I thought it wasn't that bad of an idea.You could also try to use fairly classic chips, like the Motorola 6845, but I'm just rambling at this point.I like that EPROM slab idea. Stuff like that, as I understand it, even existed in systems like Digilog (Digalog?) for PCM tape binning.

author: Gege34
author_rank: Contributor
timestamp: January 17, 2019, 10:43:12 am
content: YAMariis an OPL3 cartridge for the Atari A800 (6502 CPU).You can use a microcontroler to generate VGA output, there are plenty of examples on the web likethis,this,this.If you want to use an simple (little) LCD, you can use an SPI LCD with a microcontroler (your PIC16F1939) and communicate with the 6502.

author: technix
author_rank: Super Contributor
timestamp: January 17, 2019, 11:59:34 am
content: Quote from: Gege34 on January 17, 2019, 10:43:12 amGood info.Quote from: Gege34 on January 17, 2019, 10:43:12 amMy LCD module has native 8-bit 6800 bus interface, so putting it directly on the bus is likely a better idea. I would prefer the '1939 not used for video as it is bandwidth limited. If I am emitting VGA or similar, I would instead use a dual port SRAM chip as video RAM and use an ATmega128A as the graphics controller chip. (ATmega128 has that external bus interface for fast access to VRAM.)Quote from: Ampera on January 17, 2019, 01:30:26 amAre you suggesting PIC32MZ-DA? That chip runs Linux, has a parallel slave port and a full LCD output port that can be converted to HDMI using an external HDMI encoder chip. As of the audio if I went the PIC32MZ-DA way I would not use an OPL3 since the PIC32 will also handle audio.Quote from: Ampera on January 17, 2019, 01:30:26 amI think my 14MHz chip, clocked at 12MHz, can be fast enough for that purpose. Speaking of, what is the relationship between the PHI2 clock, core clock and the speed grade of W65C02? In order for it to operate at 12MHz do I have to supply it 48MHz?Quote from: Ampera on January 17, 2019, 01:30:26 am68SEC000 at 3.3V + dual port SRAM as VRAM + STM32F429/STM32F767 as GPU?Quote from: Ampera on January 17, 2019, 01:30:26 amThe 6845 is not for this project.