That’s right Andrew, the board can be jumpered so that any bit of any port can be positive or negative upon receiving a keyboard character. Also any bit of any port can be positive or negative when the board is ready to display a character on the screen. The only hardware limitation is that the status port is one port lower than the data port. I looked at number of S-100 boards and have never found this to be an issue. (Typically the status port for Console I/O is port 0H and the data port is port 1H). What this means is that one can splice this console board into almost any S-100 system and not have to change the BIOS/monitor software. This is important because going back and redoing all the old software would be a real pain.
Because we have offloaded the status checking/latching to 74LSxx chips the Propeller can be 100% dedicated to screen display. There are no wait states put on the S-100 bus. I started with Michael Petry’s software and trimmed it down to a VT-100/VGA display only system. Even this software with only 80X24 is beautiful. Rock solid. See the attached picture.
Because the Propeller is 100% free, the software really could be updated to display many more lines and characters/line. I’m hoping somebody out there will do this. I’m just not that familiar with assembly language for the Propeller.
BTW, the only thing that I have not been able to do is display the key scan code in the left most two hex displays. The resulting ASCII codes in the right most Hex displays are fine. Again it’s because I don’t understand Propeller assembly. The Propeller keyboard translation code is written in assembly by Chip Gracey at Parallax. As best I can tell the raw scan code is in the variable “data” but I don’t know how to get it back to the Console IO spin module.
I am attaching a picture of the display.
Hi John! I put up a post on Parallax forums asking for some help on the PASM assuming it was a software problem. However, I see that in a later email today you’ve found the issue and it was a hardware related glitch. That’s great news and I guess we won’t need outside help after all! I am really looking forward to this board coming out. Also since it is so flexible it could emulated pretty much any sort of serial port and terminal, right? Just make the Spin software changes and the board emulates a legacy serial board and terminal combination? VT-100 protocol is just an arbitrary choice and could have been any terminal.
This is an immensely powerful concept and will be very popular once word gets out. Setting up the serial console and terminal is a major pain for many vintage S-100 systems and second only to setting up a floppy disk system in terms of finicky behavior. I have high hopes for the S-100 Console IO board! Woo Hoo!
Second LCD Display.jpg
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