31 Oct
2001
31 Oct
'01
6:30 a.m.
Chuck McManis wrote:
The VAX series has had PDP-11 front ends that load
microcode, run
diagnostics, power cycle the system and boot the operating system. The
D-series of machines from Xerox had microcode that was loaded from floppy,
the IBM 360 machines did an initial microprogram load from floppy, the DEC
10 series had a PDP-11/40 as its console server, there are others. Its a
tried and true technology.
I knew most of that, I thought you had a specific web page you got your
material
from
This question doesn't make sense, if you want a
front panel design it in,
if you're talking about actually manipulating the bits in the FPGA then use
another FPGA to make a JTAG front panel.
I was referring to the CPU design and Instruction Set. A hard reset
causes a
bootstrap program to read in off the serial port. I configure the FPGA
from a
host PC. The cpu is a 12/24 bit design.
Bootstrap format:
oooo, octal data
oooooooo] octal address load
oooooooo\ octal program start
<cr><lf> leader/white space
Perhaps we're quibbling semantics. The role of the
PIC in my design is as a
serial port, and it has the ability to program serial EEPROMs so I don't
need a special cable to reload the FPGA data, I just power cycle with a
jumper set.
A handy feature.
I guess you lost me here. You're saying that the
FPGA configuration PROM
was disconnected from the FPGA and that was hard to debug and so having an
8 pin PIC chip on board to run diagnostics for you in this sort of case is
worthless and antithetical to your design goals?
You still have to program the PIC. The fault was with the general memory
bus,
not the FPGA configuration.
In my case I actually needed the ability to add op-codes and
peripherals on
the fly so I don't use PROM. In the mean time I
down load new EEPROM
configs on the fly and reset and go, easy to debug and can be shipped as
final hardware as well.
Fancy stuff there.
How is this any different than a PDP-11 where the
microcode store might
have more bits than main memory? Its one 8 pin part to hold the
configuration information and one 8 pin part to control it.
I used a PDP-8/e and a PDP-S all in one BOX computers. :)
It is hard to get use to several meg of bits in a 8 bit package when you
still
remember using core memory.
Ben Franchuk.
--
Standard Disclaimer : 97% speculation 2% bad grammar 1% facts.
"Pre-historic Cpu's" http://www.jetnet.ab.ca/users/bfranchuk
Now with schematics.