Chuck Guzis wrote:
I remember the 1130. What are you doing for a card
reader? I recall that the 1130 could only read column-binary--it was up to software to
interpret the data into character codes.
Has anyone done an FPGA emulation of the 1620? That
one has a soft spot in my heart to the extent that I can still remember the numeric
opcodes for many instructions. The 1401 occupies a similar place in my memories. Little
IBM boxes were really cute.
At the moment, I use a high speed stream protocol over USB, via the brilliant fpgalink
library by Bruce McClelland ( http://www.makestuff.eu/wordpress/software/fpgalink/
) to a
bit of python code on a PC which takes files and sends them as card column signals to my
2501 reader emulation logic in the fpga. I am mapping all the signals from the 2501 to the
adapter circuits in the 1130, timing everything and modeling state as close to a real 2501
as I can determine, so that it appears that the photocells are detecting holes at the
right time as the card virtually slides through the emulated transport, but the content of
the columns that get turned into lights are stuffed into a FIFO by the link from the PC.
However, someone has offered a small card reader that I will be gratefully accepting and
utilizing. I plan to map the real reader as the 2501 and use my alternate 1442
reader/punch emulation over the fpgalink channels so that I can both read real cards and
read files on the PC as virtual cards.
Yes, the 2501 just delivered to the 1130 one bit for each of the 12 card rows, exactly
what was punched in that column. The 1130 programmer would convert the Hollerith coded
characters into whatever other coding they wanted in their program. Boot mode wired the
signals a bit differently to provide a 16 bit result to the 1130 that was usable as
initial program load instructions, that is done in the 1130 adapter logic, not in the
2501. Finally, various forms of binary coding were used in the 1130, such as the user
program format and a special binary mode used by diagnostic programs, but all of those are
just the status of holes in a column sent as 12 bits plus 0000 to form an 1130 word. My
python program converts ascii files to Hollerith, as well as delivering binary mode files
directly as card hole images.
I don't personally know of any fpga emulations of 1620 machines, but there are
excellent simulators available.
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