3 Feb
2010
3 Feb
'10
12:09 p.m.
One of the more common chips used for async (as well
as sync) back
then was the Signetics 2651 (and 2661). A 28 pin package, simple to
interface, with a built-in baud rate generator. The successful
orphan of the 2650 CPU family.
On the 6800/6809/6502 bus, I much prefered the 6551 to the 6850. The
former included a baud rate generator, and just needed an external crystal.
I seem to rememebr a Rockwell dual serial chip for this bus, but I can't
remmebr the number off the top of my head. AndI mentiond the 6852 and
6854 in an earlier message.
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.
There were many other comm chips by the major makers,
but these two
packed a lot of bang-for-the-buck.
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 controlling it.
There were the well-known 40 pin dumb UARTs (6402, AY-5-1013, etc). They
had the advantage that they could easily be used without a procesor,
althogh interfaceing them to a microcomputer bus was very easy if you
wanted to do that.
There was a pair of chips from Western Digital, the PR1472 (receiver) and
PT1482 (transmitter). They were a bit like the dumb UART in that you
could easily configure them without a processor (but again you could
easily link them to a processor if you wanted to), but they did both sync
and async modes. HP used them in the fancy serial interface for the 9830
(HP11284 IIRC), and in the HP59403 HPIB common carrier (modem) interface.
-tony