6502.org

https://youtu.be/MrbVL-Fe7Xw

And a credit in there for Mike, too.

Neil

The 6500/1 is an interesting early device.

On a tangent, there is this piece on hacking the 6500/1 in the CBM VC1520 printer:

https://e4aws.silverdr.com/hacks/6500_1/

Extracting the code from the device, a complete IEC interface and print controller and chr set, implemented in 2048 bytes of Rom and 64 bytes of Ram.

It's a cute printer and definitely useful for the retro-computing purist.

I was curious how the ROM on the 6500 was programmed and did a Google search looking for the 6500's original data sheet. Unfortunately, all the 6500 searches turned up the data sheets for the 6500 family which didn't include the 6500/1.

My guess is it could be a PROM with fuses that are burned, or a mask ROM physically "masked" onto the chip during its fabrication.

I'd agree with either suggestion; cheaper to mask program it once it works. I found a page describing how one might get the data out of the rom, though there's no suggestion that it's programmable: https://e4aws.silverdr.com/hacks/6500_1/

Neil

Edit: Doh. Just realised that was a link already posted.

It'll certainly be mask ROM, for cost reasons - simpler technology, smaller die, higher yield.

I'm not sure if the 6500/1 was a MOS design or a Rockwell design, but the Rockwell version has a lot more documentation. This includes emulator devices with a piggyback socket for an EPROM, for development, and I think there is one packaged with extra pins for an external bus for a ROM only. They are in the Rockwell databooks and I think the Rockwell 6500/1 data sheet is in the files section here.

I checked and there are a few useful data sheets on 6502.org, including two MOS ones:

http://www.6502.org/documents/datasheet ... r_1981.pdf
http://www.6502.org/documents/datasheet ... t_1986.pdf

MOS also had a version labeled 6570 which was used as the keyboard microcontroller on quite a few Amiga's, including the original Amiga 1000.

Only the Rockwell emulator data sheet:

http://www.6502.org/documents/datasheet ... n_1987.pdf

I don't know why Rockwell never produced FLASH microcontrollers, it would have made them a lot more popular. Even for their modem chipsets which sold in the millions (just a guess) they used an external EPROM or FLASH. Some of their microcontrollers had FLASH programming routines in the ROM even.

Nice, thanks for the link.
I dumped the MOS 6500/1 in the Alphacom VP42 printer a few years ago. At the time, there were some doubts about whether the VP42's ROM could really be only 2K or if MOS had a version of the 6500/1 with more ROM. To find out, I disassembled the ROM. I also came across the 6500/1 from a similar printer, the Alphacom Sprinter 40, and disassembled that one too.

Both printers really are implemented in only 2K ROM and 64 bytes RAM. The features are impressive given the constraints:

Alphacom VP42

• Commodore IEC serial interface
• Embedded character set with 159 glyphs
• Full PETSCII support (all characters, uppercase, lowercase, reverse, quote modes)
• Control codes (PETSCII modes) and IEC secondary addresses (e.g. set page size)
• Unidirectional printing
• Self-test mode

The VP42 can print character graphics only (no bitmap graphics mode). There is not enough room in the ROM for a bitmap graphics mode. The character set data and associated PETSCII conversions occupy roughly half the ROM space.

Alphacom Sprinter 40

• Selectable Centronics or bit-banged RS232 serial interface (110-9600 baud)
• Embedded character set with 95 glyphs
• Control codes (speed control, multi-line feed, form feed, right justify, pagination)
• Bitmap graphics mode
• Bidirectional printing with speed control
• Self-test mode

Some of you will probably have fun reading the disassemblies so I have attached them here. I'm going to put these on GitHub soon and will edit this post with a link when I do.

I miss those old-fashioned printers of that era. Besides being well engineered (given the constraints) and built like tanks. They predated the modern razor and blade marketing strategy of modern ink jet printers.