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My 8052 ISA project

Although the hardware for this project is more or less complete, I am not going to do any more development on this project any time soon, I have more interesting ventures ahead. It turned out that quit a lot of folk was interested in schematics, so I made it available. Its a 100K GIF, 1256x1843 pixels. Click here to see or download.

ISABAS board image
As you can see, this one is built with all wires under the board, leaving the compnent side looking nice and clean. I was using regular 30AWG kynar insulated wire-wrap wire for interconnects after routing GND and VCC with thicker wire from phone cable. ISA interface is built using 8255 for extra control and address wires, pair of 74374's for capturing high byte of 16-bit data bus, and some glue logic for bus timings. 8052 MCU runs a bit overclocked from 14.31818 MHz which is and OSC frequency on ISA; ISA bus clock is OSC/2. The keyboard interface socket is empty, but is meant for PIC16F84, running at OSC/4. PIC will talk to keyboard, decode keystrokes to ASCII, and make them available in parallel form via one of the 8255 ports. I plan to fill the empty sport at the bottom of the image with 8-pin RTC either from Dallas or Philips, whichever I get first. Ideally, I will convert all the glue logic to Xilinx CPLD, leaving only MCU, MAX232, RAM/ROM, 8255, and PIC to surround it. Most of this stuff is experimental anyway, and you can freely leave out modules you don't need, if the high chip count makes you dizzy. I have currently tested it with 8-bit ISA COM port card, and was able to successfully send data via UART on it, so the principle works. I plan to build VT100 terminal out of this prototype, PC keyboard, VGA card, and monitor.

 

 

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