CRC65, A frugal 6502 SBC

[floobydust]

Re: Retirement: As I like to say, "time flies, fun optional". Seems like you're managing the fun aspect as well.

I've also built up multiple boards every time I design a new one. In general, I usually end up doing a second revision of every board, as I always end up with something that was either wrong, didn't like, or changed my mind. Here's a pic of four of my C02 Pocket SBCs. I ran 3 boards 24/7 for almost 3 years. The 4th board (ZIF socket) was my active development board. Once I make an update, I re-program the EEPROM on the other three and continue long term testing.

My Monitor code has a macro facility... so I can stack multiple commands and then have it loop endlessly for testing. It is limited to 127 bytes, but you can fit a fair amount of commands, etc., in 127 bytes. I also coded a 16-bit loop counter which is an option for the macro facility.

I like the board you've done... looks really good. Have your thought about trying a standard 2.5-inch IDE drive (also 44-pin connector) with the board? I have a bunch of smaller capacity drives, so I'll likely start using some of those in the near future.

[maded2]

plasmo wrote:

The CPLD is Altera's EPM7064SLC44 which is obsoleted part. Atmel has a Altera-to-Atmel converter, POF2JED, which should convert the Altera programming file to program Atmel's equivalent (ATF1504AS) I will put out an order to Mouser for few ATF1504AS and an Atmel programmer so I can check out the file conversion.
Bill

I've the ATF1508AS and the Atmel programmer so will be testing out the POF2JED on the 68000 build soon. Also, I just got a DC-DC Power controller so that I can produce the 12.5V needed to test the JTAG unlock on the EPM7128S that you did. Hope it works as I've got 8 JTAG locked EPM7128S.

[plasmo]

floobydust wrote:

I've also built up multiple boards every time I design a new one.

Given the murky supply chain for the retro hobbyist electronics, it really is a good idea to build multiple boards to prove out a design and then periodically build a couple boards during the life of the product. The question is "what to do with all these boards?" Looking at my man-cave full of assembled boards, I know I don't have a good answer to that question, although I have regularly auction off my boards on eBay starting from $1, but writing the detailed description is taking too much of my free time, so I don't do it much. I'm a bad salesman, so be it!

I'm unhappy with the ZIF socket connections so I'm building up board #6 to check out some 6502 parts from eBay. I'll give away the remaining 4 blank pc boards.

floobydust wrote:

My Monitor code has a macro facility... so I can stack multiple commands and then have it loop endlessly for testing. It is limited to 127 bytes, but you can fit a fair amount of commands, etc., in 127 bytes. I also coded a 16-bit loop counter which is an option for the macro facility.

My monitor is primitive, but I use TeraTerm's Macro capability to automate testing.

The spinning harddisk should work, but I don't have many on hand. I do have plenty of disk-on-module I can try.
Bill

[plasmo]

maded2 wrote:

I've the ATF1508AS and the Atmel programmer so will be testing out the POF2JED on the 68000 build soon. Also, I just got a DC-DC Power controller so that I can produce the 12.5V needed to test the JTAG unlock on the EPM7128S that you did. Hope it works as I've got 8 JTAG locked EPM7128S.

I'm interested in your results with POF2JED conversion as well as the unlocking of JTAG. Tomorrow I'll place an order for ATF1504AS and Atmel programmer, so I should also have POF2JED result by the end of the week.
Bill

[plasmo]

Anyone in USA interested in trying out CRC65, I'm giving away 3 blank pc boards. Send me a message with your address and I will mail it out in the First Class letter envelop.

Bill

PS, I can do a group buy if there are more interests. I can provide the essential components at the following price (shipping price not included, but is about $4 in USA):
* PC board, $1 each
* Altera EPM7064SLC programmed, $3.
* CF disk programmed with system software, $2
* voltage supervisor, 50cents
* (optional) CY7C109 assembled, $3. Note: CY7C109 is a SMT SOJ32 device available from Mouser for $3, but if you like me to solder it down on board, I can do that using parts from my stock and charge you the same $3.

You can provide your own 6502 CPU, sockets, oscillator, CF interface adapter, resistors, capacitors, misc hardware probably better than I can. You should be able to build a CRC65 for $20 of parts, cheaper if you already have your own 6502 CPU which is the most expensive component.

PPS, a note about clock frequency; while it is designed to run at 14.7MHz, if your CPU can't run that fast you can use a lower frequency clock with corresponding lower serial baud rate:
7.3728MHz clock --> 57600
4.9152MHz clock --> 38400
2.4576MHz clock --> 19200
1.8432MHz clock --> 14400
-----------------------------
PPPS, if you like me to include some core components above and beyond the free pc board, I've already listed the component cost above so you can pick and choose the parts you wanted. The pc board is still free. The shipping charge will now be $4 in USA.

[maded2]

plasmo wrote:

maded2 wrote:

I've the ATF1508AS and the Atmel programmer so will be testing out the POF2JED on the 68000 build soon. Also, I just got a DC-DC Power controller so that I can produce the 12.5V needed to test the JTAG unlock on the EPM7128S that you did. Hope it works as I've got 8 JTAG locked EPM7128S.

I'm interested in your results with POF2JED conversion as well as the unlocking of JTAG. Tomorrow I'll place an order for ATF1504AS and Atmel programmer, so I should also have POF2JED result by the end of the week.
Bill

I can confirmed that POF2JED working well. I've managed to programmed ATF1508AS after generated the JED file from the POF output from Quartus. What took the time was that as my PC is running Linux; I had to install VirtualBox with Windows10 along with all the Atmel tools.

I will attempt the JTAG unlock again on the EPM7128S this week. Just need to build a clean board with PLCC84 socket and 12V to OE1.

[plasmo]

Thank you, that's helpful information. I've placed an order for faster Atmel ATF1504AS CPLD (7ns) I want to see if I can run CRC65 to 25.175MHz with faster CPLD and RAM.
Bill

[plasmo]

CRC65 has a modified RC2014 expansion bus; it is a single-row of 39-pin right-angle male connector. The pin assignment for address, data, power are the same as RC2014. Many of the controls signals are also the same. The few different signals are 6502 specific. See photo 1 for signal assignments.

For RC2014 boards that use CPLD for decoding, it is easy to change the CPLD equations to accommodate CRC65. Photo 2 shows CRC65 plugs into a RC2014 backplane driving a CPLDTIL display board. Similarly the existing RC2014 prototype boards and VGA video board also can be modified for CRC65.
Bill

Edit, the following are links to RC2014 boards mentioned above:
CPLDTIL, https://www.retrobrewcomputers.org/doku ... mo:cpldtil
VGA video, https://www.retrobrewcomputers.org/doku ... asmo:vgarc
Prototype boards (many versions), https://www.retrobrewcomputers.org/doku ... rt#protorc

[okwatts]

Hi Bill
Still awaiting delivery of the parts to build a CRC65 but looking to see what else is proposed for the board and peripherals. I have one of Steve Cousins SC130 RC2014 boards with the SC129 IO card.. Would be interesting to get one of your Proto3 boards and possibly the VGARC but CPLD is a closed book for me. I see you can get the ATMel chips from Digikey however designing and programming will be a challenge. Retirement does provide the time, although the brain is a little less nimble these days, stretching it may take more time than is available!
Larry

[plasmo]

Larry,
I'm in the process of updating the CRC65 homepage with compatible boards and daughterboards. Currently there are two I2C daughterboards: 1), a RTC prototype based on PCF8563 that provides time and 64Hz interrupts; 2), 128x64 OLED display readily available from eBay. The I2C interface can also drive pixel-addressable RGB LED based on WS2812B.

I am modifying several RC2014 boards for CRC65:
1. LED display board as described in Jan 26, 2021 post in this thread.
2. 65SPI board described here: viewtopic.php?f=4&t=1265&start=90#p81648
3. I have looked into modifying VGARC for CRC65. In the process I'm reminded that VGARC used the 16-bit I/O addressing of Z80 which is a non-standard addressing method. To make it work with 6502, I need to make 4 cuts and 4 jumpers as well as changing the CPLD equations. In the near term, I will make the cuts and jumpers to check out the design, but long term solution is a new VGARC pc board specifically for CRC65.
4. I'm currently working on a slave 6502 processor for CRC65. Hopefully I have something to show this weekend.
5. Quad serial board may be another CRC65 compatible board with small modification.
https://www.retrobrewcomputers.org/doku ... mo:quadser

I don't have Steve Cousin's SC129, but looking at SC129 schematic I think the digital output part should work. The digital input won't because 6502 does not have separate read strobe and write strobe. When you have CRC65 working, I can walk you through the process of getting SC129 working with CRC65.

ProtoRC3 should be a nice prototype board for CRC65, but CPLD can be a steep learning curve. I'm happy to give you a hand if you want to try CPLD design.
Bill

Edit: forgot to mention that a modified ALLCF board can plug into CRC65 to drive 320x240 LCD as described here:
viewtopic.php?f=4&t=6480&start=15#p81707

There are lots of prototyping activities involving CRC65, but currently no production level pc boards that are compatible with CRC65.

[plasmo]

I have a number of salvaged disk-on-module (DOM) that are too small (32MB) to be useful. However, in this case, 32MB is the whole world of 6502 software. Like CF interface, DOM interface is also a 44-pin, dual-row 2mm connector, but the pin assignments are mirrored. So some manual wiring are required to flip the top & bottom connections. With these modifications, the DOM works nicely. It is also more compact than CF disk as shown in the side-by-side photo.

[GARTHWILSON]

plasmo wrote:

I have a number of salvaged disk-on-module (DOM) that are too small (32MB) to be useful. However, in this case, 32MB is the whole world of 6502 software.

Back when I was only using DOS, my first PC had a '286, 1MB (not GB) of RAM, and a 32MB hard disc. I never got it more than about 20MB full. I had the CAD and lots of PCB files on it, two assemblers, two text editors, and lots of source-code and other files for the things I had done in my work, all the manuals for the products we were selling, email, and more, and never got it past 20MB full—until I tried loading Windows 3.1. Suddenly I needed a much bigger disc. Then came '95, '98, and now Linux (which was a breath of fresh air after all the Windows problems). So yeah, 32MB should be fine for a 6502!

[drogon]

plasmo wrote:

I have a number of salvaged disk-on-module (DOM) that are too small (32MB) to be useful. However, in this case, 32MB is the whole world of 6502 software.

FWIW: The filing system on my Ruby boards has a max. volume size limit of 32MB - same as Apple ProDOS (which it's closely related too) As yet I've not even come close to filling it..

e.g. my main BCPL work volume:

Code: Select all

% *dir 
sd1: Free: 65221/65536: 99%

(the numbers are blocks of 512 bytes)

-Gordon

[plasmo]

Bootstrap from CF disk makes sense for a Z80 computer since it almost always has CP/M and the associated mass storage. A 6502 computer does not need all the storage, but having a CF disk may open the door for a disk file system. A 14MHz 65C02 runs like a 30MHz Z80, so a disk operating system seems well justified.

So is your filing system available to porting to different 6502 SBC?
Bill

[drogon]

plasmo wrote:

Bootstrap from CF disk makes sense for a Z80 computer since it almost always has CP/M and the associated mass storage. A 6502 computer does not need all the storage, but having a CF disk may open the door for a disk file system. A 14MHz 65C02 runs like a 30MHz Z80, so a disk operating system seems well justified.

So is your filing system available to porting to different 6502 SBC?
Bill

Mine? No, not right now. Part of the issue might be that it's written in C and runs on the ATmega1284p host processor to the system. I'm in the process of writing a new filing system for my Ruby816 system, however that will be written in BCPL, so in reality no-use to anyone but me.

If I were to do someone native to the 65C02, I'd look at Apple DOS 3.3 and partition the SD/CF/DOM into 'volumes' that was the limit of Apple DOS 3.3 - that will need about 8KB of 65C02 code, possibly less (2KB was the timing critical RWTS code in DOS 3.3) or look at one of the Acorn Disk Filing Systems (DFS) that existed on the BBC Micro. IIRC that the original DFS was 8KB (or less) but the Advanced DFS was bigger - nearly 16KB.

The advantage of the BBC Micro had for this was it's "Sideways ROM" system - essentially it had up to 16 x 16KB ROMs in the $8000-$BFFF region, so writing a disk or network filing system did not impact on memory usage - the operating system took care of bank switching, etc. so BASIC (etc.) also lived in the same $8000-$BFFF space, while the Apple II needed to dedicate about 10KB of real RAM to run DOS 3.3.

-Gordon