HP-19C Print

[teenix]

Hi all,

I'm not sure if this is a bug for the HP-19C or just my emulator, however under certain conditions, the printer fails to print.

An example is...

Turn calculator ON and into PGM mode.
Place the printer switch to NORM position
Press any keys, say EEX CLx ENTER
Switch back to RUN mode
Press [g][RTN]
Switch printer to TRC mode

Press SST any amount of times
The printer should print the executing program step but it doesn't

Press [g][RTN]

Press SST any amount of times
The printer now prints ok.

I traced this down to a value in RAM that doesn't get set when just using the SST button, however it does for [g][RTN] or any other function like [-][+] etc. Pressing numbers does not affect this setting either.

This RAM value determines whether the printer will print.

I cannot confirm this as I do not have a working 19C. If anyone else can confirm a real 19C does this, great, otherwise I have to play with the emulator.

cheers

Tony

[Joe Horn]

I verified your observation on a real HP-19C. Not only do SST and digits fail to set the TRACE mode flag, as in your emulator, but so do BST and GTO . nn from the keyboard.

EDIT -- Single-stepping a PRX does work (X is printed) BUT further single-stepping of ENTERs does NOT print, when the TRC flag is off and the printer switch is on TRACE. How bizarre is that?

[teenix]

Thanks for the confirmation, Joe :-)

Looking into it a bit more, RAM register $2E nibbles 4 and 3 are not always updated by the [keys -> a] instruction for the printer setting, and these nibbles control the printing.

43
10 = Manual
01 = TRC
00 = NORM

The only times it gets updated in Microcode is during a function key press like [+], [ENTER], [f][SIN] etc., not SST or BST etc.

The [Keys -> A] instruction is used on the 19C (of which there is only one instance), because the printer switch NORM and MAN connections appear at the ACT where the keyboard would have been in other non-printing models.

cheers

Tony