On 3 Feb 2010 at 20:09, Tony Duell wrote:
Another
popular chip used was the Intel 8274 dual-channel chip,
basically a clone of the Z80 SIO chip.
I didn't think they were that similar... IIRC the 8274 is very similar
to the NEC7201.
The uPD7201 *is* an 8474, just with NECs own part number. This
scheme obtained with most x80 and x86 support chipsets. Why NEC used
its own numbering is an unknown.
Compare the programming information for the Z80 SIO (Z8441) and the
8474. The register definitions line up virtually bit for bit. I
received a job to do some 8474 programming and noticed right away
that I could just about work from the Z80 SIO datasheet which I had
from a previous job. I believe the same person
designed both chips.
In that respect, the Z8530 bears a certain family
resemblance.
There was obvisouly the 8250 (Intel) used in the
original IBM PC Async
card, and its improved versiuons (16450, 16550, etc). For some
inexplicable (to me) reason, HP used the 8250 on the simple RS232 cards
for their HP9000/200 machines (which were 68000 based). The
more complcated serial card used a Z80-SIO with a Z80 CPU.
ISTR that the 8250 was originally a National part, not an Intel part.
Televideo used the 8474 on its early RS-422 network system
(InfoShare, which I believe was done by Novell or whatever its
predecessor was named).
The brain-dead (async only) Z80 SIO is the Z80 DART. I don't think
there's a corresponding Intel part related to the 8474 with disabled
synchronous capabilities.
--Chuck