HP 71b: Oregon Digital Environmental Case

[Michael Fehlhammer]

Addendum:
I put back batteries into the 71b ( although the calculator should be powered by the OD case batteries while connected to it via card reader port, but as mentioned before, that's not enough ).
Now the calculator works reliably - I didn't realize that before because of contacting problems with the membrane keyboard. Just the ON/ATTN key is lower than the f-key next to it, this causes some difficulties in hitting the right key, sometimes I inadvertently switched off ( f ON ).
No I could examine the system a little further:
On startup obviously the built-in ROM takes over and starts the Menu program ( see pics at last post).
Maybe there is a way to prevent that and disable auto start, by setting a system flag or something, I don't know.
So I have to break the running program to get to normal HP 71b operation.

Any idea of a HP 71b expert of a more elegant solution?

Listing of the menu program shows that the two-rows LCD is written to by a new keyword: XDISP.
Fine.
Also fine: In contrast to the simpler version "OD Serialplus" this case already has available the serial drivers (BASIC keywords: SETUP and SERIAL$ ) in ROM, no additional software is needed.
Confirmed: all RAM ports ( 5.01 up to 5.04 ) can be freed and claimed, except 5.02 ( always claimed, means: part of main memory ). Somewhat strange, isn't it?