A few years ago I bought Mensch SBC on sale. It is small (1.25” x 2.25”) and has a W65C265S8QG-8, 36 pins broken out, a right angle header, and eight surface mount LEDs. It's been sitting in my parts drawer and I was wondering if anyone has a project idea for it?

(Sorry, no project ideas from me at present, so this doesn't help answer your question... but hopefully some useful pointers.)

I always struggle to remember what these newer offerings are, so I looked it up: the '265 chip is an '816-based microcontroller, with 8k ROM, 576 bytes RAM, runs up to 8 MHz, has 64 I/O lines (but evidently not all of those brought out in this case), many timer/counters, two tone generators, four UARTs. Runs at 3V or 5V.

The Mensch SBC is described here. In this case the clock is a little under 4MHz. Helpfully, the board is also named as '265QBX.

From previous threads we see that adding a 32k RAM is fairly straighforward:
Wiring SRAM to W65C265SQXB
First steps with the real board ...

See also, perhaps:
65XX SBC general help and color display help needed
New WDC W65C268QBX Board

@BigEd, thanks for the pointers. I have the parts needed to add a RAM chip, so that's first.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

@Garth, thanks for the pointer.

@Anyone.

I can connect to the Mensch SBC using the easysxb or a terminal program. I get the welcome message and I can query the register states. But when I try to use the upload program option on Easysxb the program locks up.

I would assume this works for other people, but the program is a black box so I am not sure how to proceed.

Is there a way to use the monitor from a terminal program and just type in the commands? Anyone have a reference?

As an aside. After reading all the documentation I think this board is a major missed opportunity. The LED's aren't all that useful, but the Chip Select signals would have been really useful. A header instead of LED's would have made this board really cool.

I think this board has the standard '265 ROM monitor. WDC has a listing of it available for download.

The download command is expecting lines of S records. When it gets a valid S record, it'll echo a record count. When it gets an End-Of-File S record, it'll return & prompt for another command.

Thanks, I think their upload program is the problem, so I will try entering S records directly.

I understand what's going on.

The getting started page https://wdc65xx.com/getting-started/men ... g-started/ said to upload the .hex file, which is EasySXB's default extension. When I look at the content of the generated file it contains:


That is an Intel hex file, not S records. When you run the WDC assembler and linker it also produces a .s28 files which contains this:

That's more like it, as those are 28 bit SREC format, and that is one of the other file extensions. It's also the monitor's supported format.

So it looks like the EasySXB program is at fault because it defaults to the .hex file extension. The monitor glitches out when it receives an Intel hex file and responds with gibberish. The gibberish response causes the EasySXB program to lock up because it doesn't get the expected response. But when I try the .s28 file nothing useful seems to happen, although there are no lockups.

To get visibility into what's going on I connect to the monitor using TeraTerm and upload the .s28 file and get this output:

That is exactly the output shown on the getting started page! So I do a J 00:00C0 and the LED's change.

OK so the bottom line is that the EasySXB program is buggy and doesn't match the documentation. Not the best quality control and I suspect that most users a using the monitor via a terminal program.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I tried wiring an external static RAM. But when I try to use the monitor t read and write contents it doesn't look like it is working. The bus control register contains 01, and I believe that means the external bus is enabled.

The ram is an Alliance 128K x 8 bit. I wired the address pins and data pins to their respective pins. The exceptions being CE# (pin 22) which is tied to P17, OE# (pin 24) is tied to ground, and WE# (pin 29) is tied to WEB. I do not know which to connect CE2 to, so it is unconnected.

Does this sound correct?

Assuming that's the AS6C1008 or equivalent, CE2 will need tieing off to the supply voltage if it's not used for chip select.

Thanks. I just pulled CE2 high and the RAM worked normally in the monitor. I uploaded the LED scroll sample, did a J 00:1000 and the lights are blinking.