26 Apr
2008
26 Apr
'08
9:35 a.m.
Date: Fri, 25 Apr 2008 22:18:59 +0100 (BST)
From: (Tony Duell)
I was refering to critical timing between the hardware
control lines. For
example I've used an interface (not QIC anything) where one device
asserted a signal, then the other device had to acknowldedge within a
certian (short) time (1us or so), otherwise there would be ig problems.
The best known example of this in spades is the Pertec tape
interface. "Here's the data, catch it!" type of interface. On read,
there's a strobe asserted when data's ready, but no handshake or
other means of throttling the flow. Same for the write side--a "data
accepted" sort of signal, but the data must have been presented on
the host side. Lost data conditions aren't diagnosed, unless the
host decides to incorporate logic to do it (i.e. detect strobe before
data accepted/ready). Given that there's no standard on tape block
length, most Pertec controllers have a bunch of RAM or at least a
good-sized FIFO to deal with the condition that the host may not be
able to keep up with events. Data errors are detected by the drive,
but presented during the course of a transfer, so again, the
controller must be there to latch them when they occur.
IIRC, QIC-02 uses handshaking; QIC-36 does not.
The QIC36 ISA card I have in my junk box appaers to be
essentially a
QIC-02 host interfaxce and a QIC-02-to QIC36 bridge on the same PCB. I
keep it because the ASICs on the board are the same as those on a separate
QIC-02 to QIC36 bridge that I sometimes use with my PERQ, and thus the ISA
card is a source of spares...
The QIC-36 ISA cards I have are Wangteks--they use an 8085 and a fair
number of house-labeled ICs to do their dirty work. They're
integrated units, though I suspect there's a fair amount of shared
logic with the Wangtek QIC-36-to-02 controller, as it also uses an
8085 and has some of the same house-labeled packages on it.
My QIC-02 cards are by Alliance Technology; nothing to write home
about--just some LSTTL logic and maybe a PAL for address decoding.
About what you'd expect--and apparently clones of the Wangtek PC-02.
Cheers,
Chuck