HP75C I/O Rom Essential for HP-IL?

[pamphonica]

I've finally got my HP71B working well through an HP82169A HP-IL/HPIB interface to some testgear. Thank you Martin Hepperle for the 3D-printable connector designs so I now have enough cables!

I was wondering about doing the same on an HP75C, which does have HP-IL hardware built-in. But can I do anything with HP-IL without the I/O Rom? If not, that may make the project rather pricy! HP75Cs without ROMs are quite cheap. But I/O ROMs are rare.

(BTW if anyone in UK/Europe does have a suitable HP75C with I/O ROM for sale at a reasonable price, please contact me.)

Thanks
Jeremy

[rprosperi]

The I/O ROM is not required to do basic HP-IL operations, the 75C has core capabilities built-in, however the I/O ROM basically is required to do most non-trivial things. Also, even with the I/O ROM, HP-IL capabilities of the 71B are still better and can't be matched, though you probably can accomplish most everything you need to do.

Also, the I/O ROM adds many capabilities to the 75C beyond pure I/O features, it's really more of an I/O & Advanced Programming ROM, and you should get one if you plan to do much with the 75C; everything is easier with this great ROM.

You can explore all this using JFG's emu75 with the I/O ROM, utilizing virtual I/O with IL-Per or pyILPer to better understand how much this ROM adds. It won't let you talk to HP-IB devices, but it will let you learn more about using the 75C, which is fairly different from the 71B, despite their initially obvious similarities, while waiting to get an I/O ROM, which are relatively rare, and hardly ever cheap.

[Sylvain Cote]

Before the I/O ROM there was the 00075-13013 I/O Utilities Solutions Book who contains the HPILCMDS lex file which added the SENDIO and ENTIO$ words allowing you to send and receive raw HP-IL commands on the loop.
Sylvain
PS: you must register (free) on groups.io site and be member of the HP75 group to have access to the above link.

[vassilisprevelakis]

(09-09-2020 12:09 PM)pamphonica Wrote:  I was wondering about doing the same on an HP75C, which does have HP-IL hardware built-in. But can I do anything with HP-IL without the I/O Rom? If not, that may make the project rather pricy! HP75Cs without ROMs are quite cheap. But I/O ROMs are rare.

Hi Jeremy,

The HPILCPMDS lex file that Sylvain mentioned allows you to do most tasks you'd want to do with HP-IL. It is lower level than the I/O ROM and hence writing code for it is more of a pain.

Even though I don't have an I/O ROM I still managed to use my 75C with HP-IL controlling the 82186A modem, HP 82164A RS/232 etc.

Specifically I used the 82164A to drive a serial plotter (HP-7220C).
You can see the video and find out more about this in my youtube video at: https://www.youtube.com/watch?v=r0sL62EWkhY

Vassilis
http://www.series80.org

[sjthomas]

One of the things I truly regret selling some years back.

[pamphonica]

Thank you all for the information. I'm currently trying to get a 75C and this reassures me that I can get some of it working at least!

[Ken S]

There is an HP-75c auction on eBay with an I/O Rom starting at $125.

I have no affiliation to the auction.