HP97 The journey begins

[teenix]

Hi all,

The HP-55 CPU board seems to be behaving itself so I have made it available from http://www.teenix.org.

The CPU board crystal can be evenly divided to the original 784KHz frequency, but the one I have is running slightly fast and this appears to be due to crystal capacitive loading, so some might do the same or run a bit slow. The timer I have runs fast by just under 4 seconds over 8 hours which is a little worse than the original +/- 1.5 seconds over 8 hours.

To counter this the user can tweak the timing by enabling a software adjustment feature to slow down or speed up the timer. The adjustment has a fairly wide range and the setting is stored in EEPROM which is recalled on power up.

I have been playing with the HP-65 and HP-67 CPU boards and now all 3 CPU boards support saving and recalling the calculator state and memory.

Some calculator state examples are: the error display is showing or flashing, a program is running, numbers are partially entered etc. This feature has been added to a top level menu item in all 3 boards.

The only thing that can physically change is the position of the Run/Prgm/(timer) switch, so if that has changed, the recalled state becomes unusable. In this case a message will be displayed to inform the user. Just put the switch where is was when the state was stored, recall again, and the calculator will resume where it left off.

The updated 65 and 67 flash files have been uploaded to the web site.

cheers

Tony