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RE: [N8VEM-S100:2649] Re: A new (V2) version of the S100 Bus System Support Board

I love the PIC16F505 chip.  I've used it successfully in many designs.  Careful to not count 12 Output lines, it only has 11 I/O and 1 Input only.  The other sad thing I remember (please correct me if I'm wrong) is the internal oscillator is only 4Mhz.  To get 20Mhz operation, you must use an external oscillator.  I don't like the VCC pin 1, Gnd pin 14 either.


>An outside of the box idea is a PIC 16F505 has an internal osc, 14 pin DIP with 12 usable I/O lines and you only need 11 of them. And its about half the cost around 75 cents in bulk.  So program it, slap the power leads on, and it does its thing.

True, a GAL can process I/O ten million times faster than the eye can perceive, whereas the PIC running a tight loop and simple table lookup might only be able to process a hundred thousand times faster than the eye can perceive.  Fast enough for human I/O devices, although not for memory decoding.

Something I dislike about Microchip is they never hook up GND to pin 7.  If they did, you could program up a couple of their processors to emulate many TTL logic chip at up to "hundreds of KHz" speeds just by loading a simple program into the PIC.  I need a 7400.  No wait I need a 7402, I'll just reprogram it.  That doesn't work because Microchip always wires GND to pin 1 or something inconvenient like that.  Doesn't matter for a new design, only if you're trying to make a "7447 replacement" (other than that being a 16 pin, obviously)

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