PIC12F635PIC12F675 PIC12F683 PIC12F752
PIC12F635 can only be programmed with HVP (High Voltage Programming). This means it requires Vpp voltage (higher than Vdd) for programming. NSDSP cannot generate such voltages. Therefore, PIC12F635 requires NSHVX High Voltage Extension or an external HVP circuit.
Since release 134, NSDSP software assumes that NSHVX is connected when programming PIC12F635. It manipulates the PGM/RTS pin (LVP, or pin 6 of ICSP header of NSDSP programmers) to control MCLR state through NSHVX. Even when NSHVX is not connected, the PGM/RTS pin will still toogle during programming.
Instead of NSHVX, you can use an external HVP circuit. Without NSHVX, PIC12F635 will be programmed correctly, but it may not reset after the programming, especially if MCLRE configuartion bit is ON. In such situation, it may be necessary to power-cycle the chip, or disconnect NSDSP and manually connect MCLR pin to the ground for a short moment to reset the PIC.
Target Voltage Below 4.5V
If voltage is less than 4.5V programming is severely limited - it is impossible to bulk erase the device, it is also impossible to erase configuration bits, EEPROM, UID.
NSDSP cannot detect target voltage and it assumes that the voltage is above 4.5V. If the actual target voltage is less, programming will fail. However, if you tell NSDSP that the target voltage is below 4.5V through programming software, NSDSP will use special low-voltage programming mode. In this mode, NSDSP verifies if the desired programming can be performed at voltages below 4.5V, and if it is possible (device is not code protected, configuration bits do not change or only change from 1 to 0, EEPROM is not programmed, UID is not programmed), it performs the programming. If such programming is impossible, NSDSP software will stop and show an error message.
Programming in low-voltage mode may be considerably slower. In addition, you may need to decrease programming speed to 3MHz or below.
We have measured time necessary to program and verify PIC12F635.
|Operation||Time||Programming and Verification||1.8s||Programming only||1.7s||Verification only||0.2s|
The measurements reflect the time necessary to program/verify the entire chip, including all user programmable memory areas and very slow data EEPROM.
NSDSP cannot be used to debug PIC12F635.
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