Save/Restore Display Mode

[Dieter]

(05-20-2015 01:45 AM)Sylvain Cote Wrote:  Store display mode from the PPC ROM P.400 ...

"SD" saves flags 16-55 in a register defined by X, so that the user may then change the contents of register d (particularly display format and trig mode) during a program yet, have the capability of restoring the original format at the end of the program by by calling "RD".

SD and RD store resp. restore most of the 41C mode settings. So not only the display settings are affected (that's merely flags 28/29 and 36-41), but also printer mode (21), data/alpha entry (22/23), overflow and general error flags (24/25), sound setting (26), user mode (27), trig mode (42/43), alpha mode (48) and others.

Only flags 00...15 are not affected, which includes some internally used mode flags (e.g. 11..14). I assume this is because SD turns the content of register d into an alpha string (probably to avoid changes due to normalisation), so that two bytes of the original content are lost.

However, the important point is that SD and RD also affect many other settings, not just the display mode as their names suggest.

Dieter