HP97 The journey begins

[teenix]

HI all,

A little more on the 19C today.

Some tweaking was required for the turbo mode to manage HP functions like the printer, PAUSE and the low battery decimal point flashing. These have to operate in normal HP timing.

The battery voltage in the 19C is monitored by the Cathode Driver IC and sets a Status Flag in the ACT depending on the state of the battery. I have implemented this now and I can adjust the output of the bench supply to trigger the low battery condition and when it is below the set point, the HP microcode detects this through the Status flag and does its thing to flash the decimal point LED.

When I first had this going the decimal point LED just went dim and it took me some code fiddling to realize the turbo mode was active and it was just flashing on and off very fast. Normally this is about 300mS so it gives a hint on how fast the HP microcode can run. Normal 19C instruction execution is about 280uS, in turbo mode this can drop to around 15uS depending on the instruction and a few other processes that may have to be dealt with.

I also added a menu item where the user can set the trigger point for the battery low detect, which spans between 4 and 5 volts in steps of 33mV.

cheers

Tony