check on the atmel site for ATF15xx family of CPLD: available on PLCC 44 package , free developing/programming SW, simple PARALLEL/JTAG programming interface with schematics available some examples circuits ( amongs other there is an 'improved 8255' )
You'll probably like them a lot if you have a chance to get familiar with them. :-)
In all likelihood this was a result of the engineer's lack of experience/skills/whatever than a problem with the FPGA technology itself. :-)
I'm glad to hear you managed to get the 8255 solution working.
known workaround.
programmable logic.
You _could_ program FPGAs (and/or CPLDs) if you got a development kit for about $100.00; writing an 8255 replacement in VHDL or Verilog should be easy and fun! :-)
Or, for that matter, (at least in the Xilinx package I have) you can do schematic entry.
Have Fun! Rich
If you have an I2C port on your board, you can use this chip:
If you don't have an I2C port or there are other problems with the chip, you can use an CPLD. I've implemented the functions of the 9555 in VHDL as an example how to use my I2C VHDL implementation:
You could drop the I2C part and add an ISA interface, which should be not too difficult.
But using a FPGA would be overkill for such a simple project, use a CPLD. There are chips with on-chip flash (most FPGAs need an external flash for programming at power on) from Xilinx and Altera, like the MAX II from Altera, which you can buy for 5 euro (the smallest part should work for a
8255 replacement). There is even a development kit with a PCI interface:but you can get cheaper development kits for it, too:
Software is free for this part from Altera (same for many Xilinx chips).
-- Frank Buss, fb@frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
It doesn't say all ports are reset? Although it may work that way.
Yes; the 8255 is crap. You'd be much better off to get an FPGA or a CPLD and write your own functions.
Cheers! Rich
I was always nostalgic about the 6526 because of it's ability to configure I/O individually for each bit, until now, that I can do this with PICs. Just started playing with 16bit 18F2320 and it even has separate ('software') registers for write and read buffers. Too bad I took so long to give pics a try. OOOH baby.... HEH. Cheers.
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