| ??? 01/24/06 22:13 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#108242 - for once, I've got to agree Responding to: ???'s previous message |
With no explanation of why it's desirable to use an 8255, I've got to agree that it looks like a lot of trouble for no apparent benefit.
The 8255 is not difficult to use if one operates it as described in the datasheet. It's intended to be a bus-based peripheral. If it's attached to the bus, with the nRD and nWR lines driving it and with logic decoding the device's location in the memory map, it should be easy. If you don't REQUIRE the 8255, however, why use it? It has very little output drive, and can barely drive a darlington transistor. It's too slow for anything much beyond the speed of the original 12 MHz 805x. Nearly any assortment of output registers and input buffers would work better and more easily, and some very inexpensive programmable logic could build pretty much any combination of ins and outs that the 8255 can provide, including handshaking for less money than the 8255 typically costs. What's going on here? RE |
