3 Nov
2005
3 Nov
'05
11:32 p.m.
On 11/3/2005 at 6:22 PM ard at p850ug1.demon.co.uk wrote:
The worst, by far, has to tbe the 8255 parallel chip.
That was clearly
designed by soembody who didn't think what he was doing. For those of you
who've not read the data sheets, any write to the mode control register
clears all output port lines to 0.
For what it is and WHEN it was developed, the 8255 is a pretty good device.
There are still new products made that use it (very popular in the data
acquisition area). I can't think of any other single parallel interface
chip from the 70's that's still puffing along.
I wish the thing was faster. The NEC 82C55AC variant is good to 10 Mhz,
but that's pretty slow when you're talking about a PCI bus.
There are precious few of the really good peripheral chips from the early
days of the microprocessor that are still as useful. The Signetics 2651
USART, maybe?
Cheers,
Chuck