hrrrmmm...sorry. Techno speak mode wasn't cancelled, where it should have been....
An ISP is a tool, to low-level program an uC (microcontroller), which already is soldered
into a circuit.
Other terminus technicus: In-circuit programmer.
HVP: High voltage programmer, where "high voltage" is every voltage above 5V/3.3V (depends
on the system) and NOT something to make sparks and buzzing arcs from.
I dont know, whether are used outside the ATMEL-world.
These are tools which allows to "reset" a uC.
ATMEL chips (ATmega...) have "fuses" which one can "burn" programmatically to prevent others
from reprogramming or reading the flash. "Burning" those fuses can done with a normal, not-HV-programmer
...also accidentically...and the poor DIY girl/guy has one desktop decoration more and one chip to play/program
with less. In those cases a HVP becomes handy: It totally nullify (write zeroes/FFs) to everything, which can be
programmed of such a chip. This way, the flash contents get lost, but the hardware is saved.
Here are some examples:
https://mightyohm.com/blog/2008/09/ardu ... rogrammer/
By the way: In case of a calculator of this price tag (not meaning, that the DM42 is not worth each single EURO it costs!!!
I LOVE this gem! -- but about 200 EURO are 200 EURO) I think "learning by experience" is little too harsh -- especially for
those, who do this experience -- especially when checking for USB-power (the routine is already in the firmware) and quiting
the firmware update process if only the battery is there, seems to me a not too complicated task for a magician like David, whose
magic was one of the main reasons, why we all got these wonderful piece of technique.
Only my two cents...your currency may vary...