In PIC12C5XX programming guide I found a requirement:
1.1 Hardware Requirements
The PIC12C5XX requires two programmable power
supplies, one for V_DD (2.0V to 6.5V recommended) and
one for V_PP (12V to 14V). Both supplies should have a
minimum resolution of 0.25V.
What does it mean?
I found an article on power supply resolution versus accuracy, and it boils down to:
Our power supplies use Digital to Analog Converters (DACs) to take the user inputted settings and convert them to analog signals that set a programming voltage that will interact with the control loop of the power supply to set the output. The resolution supplemental characteristic represents one single count of the DAC.
Which means it applies to power supplies where the user sets the voltage; minimum step by which the voltage can be changed. Now in the guide we have a pretty loose requirements for preset voltages, no requirement for them to be changeable by the user. I really don't see any application of supply resolution as explained by the article. The basic requirements look like if I apply 5V and 13V with accuracy +-1V I should be set. So what does the resolution mean in this context?
Best Answer
A programmable supply is required to make a production programmer for these PICs, because production verification must be done at both minimum and maximum Vdd for the part.
There are requirements for both accuracy and resolution of the programming, however the document does not actually specify what the tolerances are, just that it must be verified 'at' the minimum and maximum voltages, which is clearly an impossible condition to meet.
It's left up to the implementor whether it's better to fudge the maximum and potentially compromise the programming verification or vice versa (or just aim for the nominal and let the the chips fall where they may, so to speak).