IBM 1410 FPGA Implementation Update - new github repository
Jay Jaeger
cube1 at charter.net
Sun May 2 15:38:33 CDT 2021
The last 12 months I have been pretty busy working on my 1410 in FPGA
project, and there is now more to share, though I have not done much
actual work since February - been too busy playing with other "toys". 8D
First, I finished working through all of the IBM 1410 and IBM 1415
Automated Logic Diagrams - generating VHDL and testing the results with
test benches. [Note that this includes the built-in 1401 compatibility
mode, activated at the flip of a switch.] That took most of 2020.
So, the CPU generation in VHDL is now more or less complete, and I added
a hand coded memory module for memory, as core is kind of hard to find
on an FPGA development board. ;) I am currently using a Digilent Nexys
4, but I think it might have even fit on a Nexys 2 - there is plenty of
room to spare, and there isn't anything in the VHDL aside from, maybe,
the memory implementation (though even that is pretty generic VHDL).
With this the CPU runs, at the very least, Unconditional branch (Jump),
Halt, NOP and Set Word Mark instructions seemingly correctly - I haven't
tried any others. Somewhat surprisingly, aside from issues with the
hand coded VHDL in triggers and the need to communicate pins tied to
logic one or zero, the auto-generated VHDL works untouched.
I have updated the github repository for the C# database application
that generates the VHDL from time to time (and which includes the
complete database) at http://github.com/cube1us/IBM1410SMS
There is now a *new* repository, http://github.com/cube1us/IBM1410FPGA
which holds the generated VHDL, some hand coded VHDL modules for certain
SMS cards (typically for triggers, for example), the console and test
benches I used along the way, and VHDL "Integration Tests" which are
designed to be loaded onto the board - the current one being
IntegrationTest3.
There will be, eventually, a third repository which will contain the C#
code that "hosts" the IBM 1410 console and peripherals, communicating
with the FPGA over a high speed serial over USB connection. I figured
out that this should allow me to emulate peripherals without having to
resort to sending data over Ethernet, SPI, I2C or the like. I have just
started that, so it really isn't at a point that there is much to share.
Once I have a console working (which will require a re-do of the console
VHDL implementation, which right now communicates in ASCII, but should
probably be using BCD), I should be able to pre-load into memory some of
the CPU diagnostics, by loading a diagnostic routine into either my 1410
simulator (http://github.com/cube1us/1410), or Richard Cornwell's
emulator in SimH and then taking a snapshot of "core" to pre-load into
the FPGA. At that point I expect I will be able to test the CPU pretty
thoroughly. I hope and expect that will happen this year sometime.
Unfortunately, I do not have the ALDs (Automated Logic Diagrams) for the
IBM 1414 I/O Synchronizers, but I do have the Instruction Logic Diagrams
which should allow me to code VHDL to emulate card, tape and maybe
eventually even disk functions, so those might take a while.
If anyone cares.... ;)
JRJ
More information about the cctalk
mailing list