3 Nov
2005
3 Nov
'05
3:45 p.m.
Subject: Re: That darn Intel jingle...
From: "Chuck Guzis" <cclist at sydex.com>
Date: Thu, 03 Nov 2005 15:32:44 -0800
To: cctalk at classiccmp.org
On 11/3/2005 at 6:22 PM ard at p850ug1.demon.co.uk wrote:
Z80 PIO.
However the 8255 is of the 8080/8085/z80/ and general Intel lineup and
due to that also the most widely multiply sourced. It's ugly but what
comes in to do better?
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.
D72055 the last version of the part hit 12mhz. If your going on PCI
why bother and just put a gate array to work.
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?
Well there are plenty of 8251, 8253, 8259 around, then there are the 2681s
and (gag) 8250 series.
Not many but then what do you need after lots of ram?
Allison
3 Nov
3 Nov
4:17 p.m.
On 11/3/2005 at 6:45 PM Allison wrote:
Z80 PIO.
16 measily bits of I/O in a 40 pin package. :( What a waste of real
estate.
D72055 the last version of the part hit 12mhz. If your
going on PCI
why bother and just put a gate array to work
Mostly laziness. I could probably also just buy a PCI data acquisition
board, if I didn't want Mode 2 I/O (which I do).
Well there are plenty of 8251, 8253, 8259 around, then
there are the 2681s
and (gag) 8250 series.
Well, the 8259's a CPU support chip, and I tend to think of the
8253/54/57/37 the same way. The 51's a peripheral chip that's had its
share of warts, however. The 8250 is a ridiculous National product that
can't do sync in a single-channel 40 pin package yet. The Z80 SIO and the
Intel 8274 are essentially the same chip that should have probably been
made part of the PC instead of the 8250.
Speaking of which--I've got a bunch of Z80 DART chips. I've been told that
these are really derated Z80 SIO chips. Will they do synchronous I/O or
has that part been disabled? I can't find my databook for the things any
more.
Cheers,
Chuck
5:48 p.m.
On 11/3/2005 at 6:45 PM Allison wrote:
Well, there are 2 handshake lines for each port from what I remember. So
that's 20 pins. Add another 8 for the host-side data bus and two for
power, and you've accounted for 30 pins. That leaves 10 for register
select, read/write, etc. Since there's no common package between 30 and
40 pins, it seems reasonable to me.
Z80 PIO.
16 measily bits of I/O in a 40 pin package. :( What a waste of real
estate. can't do sync in a single-channel 40 pin package
yet. The Z80 SIO and the
Intel 8274 are essentially the same chip that should have probably been
made part of the PC instead of the 8250.
I thiought there was an IBM I/O card for the PC with an 8274 on it. One
of thr two synchonous ones mentioned in the TechRef. No, I've not seen it.
Speaking of which--I've got a bunch of Z80 DART chips. I've been told that
these are really derated Z80 SIO chips. Will they do synchronous I/O or
has that part been disabled? I can't find my databook for the things any
more.
From what I remember, they are pin compatible with one
version of the SIO
(rememebr the SIO had 41 pins, really ;-)), and have the same
register
allocation. I was told they were actually SIOs that had failed on the
synchronous side, but I don't know if that logic was disabled or just not
used.
In any case the Z80 peripherals are very easy to link to the Z80, and
harder to link to something else (there's no Wr/ pin, the chip assumes
that an I/O cycle without Rd/ and without M1/ is a write, that sort of
thing).
-tony
6989
days inactive
6990
days old
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