On 03/17/2012 11:17 PM, Mouse wrote:
"Posh" is a great way to put it! The 8530 is a fantastic chip.
Isn't that the chip Sun used on most of their SPARCstations? If so, I
disagree in at least a few respects. I *think* it has basically no
FIFO, though it's possible I'm confusing it with something else - and
that fuzzy recollection is talking about the part used by Sun, and I'm
not sure whose part that was; perhaps AMD's more recent version is
friendlier. Also, to quote NetBSD's z8530reg.h (version 1.12, in case
anyone cares),
* The damnable chip was designed to fit on Z80 I/O ports, and thus
* has everything multiplexed out the wazoo. We have to select
* a register, then read or write the register, and so on. Worse,
* the parameter bits are scattered all over the register space.
* This thing is full of `miscellaneous' control registers.
The rant continues for another paragraph; I can quote the whole thing
if anyone wants.
Yup, that's the one, and, that's why it was a bad idea for Sun to use
it as a friggin' console port that will only every do 9600 8/N/1 async
ever in its whole life. ;) (well, and interface to kbd/mouse, but
that's even less demanding!)
All the "miscellaneous" control registers deal primarily with SDLC
operation, which it does extremely well.
AMD's isn't more recent or more "friendly"; it's a second source
of
the same chip. The '8530 is pretty damn friendly to being with, though.
I've done five or six designs with that chip, some of which go VERY
fast (megabits) and some of which used its synchronous capabilities. It
is extremely powerful. Whining about how to access the control and
status registers that mostly only get dealt with at initialization time
is worrying over about twenty extra lines of code. "These kids today, I
just don't know.." ;)
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA