|HP41 Card Reader can read/write HP-71 cards|
Message #1 Posted by Vassilis Prevelakis on 1 Apr 2005, 2:05 a.m.
After going through the HP82104A ROM code, I discovered that HP intended to make the HP-41 card reader able to accept the longer cards used in the HP-71B and HP-75C. The longer cards have much increased capacity (up to 160 registers per card versus 32 registers for the normal cards).
Unfortunately, not all card readers support the longer cards. I have found that only card readers manufactured after 1984 have the necessary code in their ROM.
Use of the longer cards increases the drain on the HP-41 batteries, so be aware that you need a fresh set of batteries or a newly charged NiCd pack.
The bad news is that, so far I have been unable to transfer any data between my HP-41 and my HP-71B or HP-75C. I guess the manual card readers on these machines have a different format.
Another problem I encountered was that the longer cards are narrower than the HP-41 cards, so you need to make sure that the card is placed towards the bottom of the slot. The newer card readers have little "fingers" on the top of the mechanism that ensure that the card does not move sideways, as it passes through the card reader.
The code that allows the long cards to be accessed is not enabled by default. You need to create a link on the card reader PCB. This enables the code and allows the long cards to be read.
Unfortunately my web site is currently down, but I will post pictures of the operation to enable the link as soon as possible.
In the mean time, here is a picture of a long card being VERified:
If anybody has any ideas as to why HP did not enable the code or advertise the fact that the HP-41 could use the longer cards, please let me know. I assume that they did not want to create competition of their HP-IL storage devices.