SCADA...
'On Microcode.
On Tue, 23 Jun 1998 05:21:43, Dave Eastabrook <news@elmbronze.demon.co.uk> wrote:
> (what is microcode anyway? I guess I know the sort of thing it does,
> having worked on a system that controlled its deployment and usage for
> keyboard control, and I know you can compile it or at least, linkedit it
> just like the normal stuff, but what is it? Anything like machine code?)
Microcode is machine code, this is from "Microprocessor
System Design Concepts" by Alexandridis.
"To implement the control section, either random logic (hardwired) or
microprogrammed techniques, or some proper combination of the two have
been used." ... "The instruction code is decoded to identify the
specific operation to be performed. Since each such operation is
carried out as a sequence of microoperations, multiple control steps are
required to process an instruction."
"Various groups of microinstructions, forming microroutines, are usually
incorporated into a complex system." ... "Execution of the microroutine
results in control of all fundamental operations such as data transfers
and elementary data transformations."
It is machine code but for the underlying machine. The underlying
machine is some kind of simple, fast, computing engine that runs the
microcode, the microprogram. At IML or IMPL time, if we're looking at
a S/370 145, we load the control store with a microprogram that *is* a
S/370 emulator. The microprogram then interprets S/370 opcodes.
Microprograms, microcode, while the purists will say this is different
from code for microcomputers, it really isn't. It's all just code. If
you can read and write S/370 machine language, you can read and write
microcode, it's just different low level language and specific to the
underlying hardware....
Except, some people are using C, PL/M and in our world, PL.8, as
microprogramming languages.
In theory, (again to a purist), you're a microprogrammer if you drive
the hardware gates directly, opening and closing paths through the
hardware logic.
In practice, as you pointed out, you're probably programming in a high
level language and using a cross compiler anyway... so what's the diff?
My guess on the FAA 3083 issue is that IBM has some customized microcode
in the IO part of the 3083s. Those things had channel directors as I
recall. IBM probably implemented back level support to maintain
compatibility with either the RADAR or the displays. I don't think the
Y2K problem is in the channel. I read last year that it was in the
system control and data acquisition subsystem. There's that word again,SCADA.
Given the vintage, the 3083 microcode development environment probably
was a macro-cross-assembler running on S/370 TSO. This is speculation
but how I'd do it. It could even have been IFOX00 with a custom
SYS1.MACLIB, again, that's how they did it in those days.
But hey, what do I know, we have people here who are happy to mouth off
and call me clueless. ...so I suppose, clueless I am... even though
I've seen teams do exactly this kind of programming... in mythic times, that is.
cory hamasaki 556 days.
See also, vertical microcode, horizontal microcode, nanoinstruction,
intramodule control signals, multiple phase clocks, control state
generator, bit-slice, polyphase, macroinstruction.
x10.dejanews.com
'Subject: Re: FAA have stated they'd be done fixing in a few months.
From: kiyoinc@ibm.XOUT.net (cory hamasaki)Date: 1998/06/24
Message-ID: <7kepWhCNP4qd-pn2-dDzZShpPWUTQ@localhost>
Newsgroups: comp.software.year-2000[More Headers]
[Subscribe to comp.software.year-2000] |
