Validation Test
Remember that validation test suite I wrote last December? Back then, I ran it using a Verilog hardware simulation of BMOW, and it exercised every variant of every machine instruction: adds, jumps, xors, loads, stores, branches taken, branches not taken, branches forward, branches backward, branches across a page boundary, and on and on in mind-numbing variation. Now I have that same test running and passing on the real BMOW hardware! OK, I had to cheat a little and disable the stack-related tests, since I still haven’t wired up the stack pointer register. But the other 95% of the tests run perfectly and the LCD says “pass”. Things are really looking good!
The stack pointer is the next obvious step. I’m a little hesitant to do the wiring, since the last two pieces of hardware that I added each made the machine stop working, and led to frustrating debug sessions. Hopefully this time will go better. Then the core “computing” part of the computer’s hardware will be done, and I can begin on I/O (keyboard, USB) and the real-time clock.
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I dont know what kind of USB headache you might manage to come up with. The only sane way I can think of tackling that is a FTDI chip and microcontroller. Some of the atmel microcontrollers have built in usb interfaces too. This will be interesting to see
Yes, I’m planning to use a USBMOD4, a 32-pin module with an integrated FTDI chip and USB connector. Check out the “Devices” page of the schematics document from the Technical Info page.
I did some tests with it on a breadboard a few months ago, and it looks easy to use. Connect the USB, open Windows HyperTerminal, and type a letter. The read ready flag on the USBMOD4 goes low. Then when your CPU brings the output enable flag low, the USBMOD4 drives the letter byte onto the bus. For output, your CPU can just write to it like a RAM or UART.
http://www.futurlec.com/USBMOD4.shtml
I’ve used the Advanced serial port terminal by Eltima Software program to connect.
If I remember right, the driver I got from ftdi makes their chip looks like a serial port to windows, so I use this program to read/write data over usb.
And that USBMOD4 is parallel, what a find! I would find that loads easier than shifting bits out one at a time when you can dump them all out and let the usb chip take care of Parallel to serial.
So we have some relatively old computers at work. Once I have the space, I’ll probably take one home and see what I can do (all ISA bus)
Also, some things that can be used for connecting modules without expensive headers and connectors and all is just fit them into PCI slots (or ISA now that I think of it)
Backplanes are the way of the future