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Since NSDSP is a Low-Voltage Programmer (LVP), it can only program PIC devices if LVP configuration bit is enabled. Fresh (unprogrammed) devices have LVP bit set and therefore they can be programmed. It is impossible to disable LVP bit during LVP programming, but if the device has been previously programmed with HVP programmer, the LVP bit may have been disabled.
When brown-out is enabled with BOREN configuration bit, LVP is only possible when the VDD voltage is above the brown-out threshold.
These limitations may be avoided with High-Voltage Programming (HVP), however NSDSP requires an external circuit for HVP. Microchip programming specificatons for PIC16LF628 require that VPP is applied to MCLR before VDD. Since NSDSP does not have any control of VDD, this requirement cannot be satisfied, however, in our tests the HVP programming has succeeded even without VDD manipulation. Therefore, NSDSP software, starting release 126, supports HVP programming for PIC16LF628.
Be careful. It is possible to brick PIC16LF628 with HVP programming if each of these three conditions is met:
Target Voltage below 4.5V
If voltage is less than 4.5V it is impossible to bulk erase the device. Unless the PIC device is code protected, NSDSP still can program the device, however, without the bulk erase it takes longer.
NSDSP cannot detect target voltage and it assumes that the voltage is above 4.5V. This ensures fast programming at usual voltages. However, if you want to program at voltages below 4.5V, you must specify the actual target voltage through programming software, or the programming will fail. If you specify the voltage below 4.5V NSDSP will apply special programming algorithm, which does not use bulk erase, but is slower than the regular algorithm.
If you are programming a device which is code protected, NSDSP cannot remove protection if the voltage is below 4.5V.
When programming at voltages below 4.5V, NSDSP tries to save time, and therefore does not erase memory areas which are not being programmed. If such erasing is needed, you can erase the device manually before programming.
NSDSP cannot be used to debug PIC16LF628.
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