HP-19C Repair Odysee

[PANAMATIK]

(07-05-2021 11:35 PM)teenix Wrote:  In this case, the PIK chip automatically does the print carriage home as the printer home test instruction (PIK1120) does not execute by the ACT on the HP-19C or HP-97 at switch on.

This was also confirmed on my 97 CPU board.

cheers

Tony

That is correct, but let it more precise:

At power up the ACT reads the initialization instructions from ROM. When it encounters the pik_home? test instruction, the PIK chip executes the instruction and tells the ACT if HOME switch is activated or not. If not , the ACT branches to code which invokes the pik_cr? instruction, which let the PIK start the motor until a debounced negative edge occurs on the HOME input, i.e. HOME position is arrived.

ACT and PIK and ROMs must be OK to perform the correct HOME return movement.

Bernhard