A functional difference between the 41C Full- and Half-Nut LCD driver?

[J-F Garnier]

(10-13-2022 09:08 AM)J-F Garnier Wrote:  

(10-13-2022 07:51 AM)Ángel Martin Wrote:  As it turns out, there's a difference in the way the [SPLASH] routine works between the FULLNUT and HALFNUT LCD drivers. Unfortunately I have no idea why this happens (which is not supposed to!), but the good news is that I figured out the code changes needed to make it work properly on each type.

We already discussed this problem previously, unfortunately with no definitive conclusion on the cause.
I don't believe there is a difference between the FN and HN LCD drivers, except the extra characters of course.
I'm more suspecting a problem in the driver emulation in the CL. But I don't own this machine and I will not investigate myself.
Someone with non-CL FN and HN machines may confirm that there is no difference relative to the SPLASH screen behaviour between FN and HN.

(10-13-2022 10:03 AM)Sylvain Cote Wrote:  With LIBRARY4 in page 4, OSX3 ROMs (4 banks) in page 8 & 16CS ROMs (4 banks) in page 9.
On the 41CX-FN, I get → "XROM:16:00 → "¯ -LIB#4-R ."
On the 41CX-HN, I get → "XROM:16:00 → "-LIB#4-R60b."

With LIBRARY4_CL in page 4, OSX3 ROMs (4 banks) in page 8 & 16CS ROMs (4 banks) in page 9.
On the 41CX-FN, I get → "XROM:16:00 → "-LIB#4-R60 ."
On the 41CX-HN, I get → "XROM:16:00 → after some characters scrolling the screen goes blank and freeze

So I may be wrong but that's even more interesting: a undocumented functional difference between the FN and HN LCD drivers?

And that's interesting for all developers of HP-41C emulators: how do the 2 LIB4 versions behave with the existing emulators?
Ángel, it would help if you could document the difference between the two LIB4 code versions.

J-F

[Ángel Martin]

Yes, Sylvain's tests confirm there's an actual difference in the way the LCD is managed between FN and HN machines.

See attached the actual code. The only difference is in instruction at 9x4750:

the FN version uses JNC-43 instead of JNC-44, and therefore skips (i.e. does not execute) the READ 14(d) instruction at 0x4724 within the [NXTCHR] loop.

As per the emulators question, the HN version works like a charm on V41 and DM-41X.