Electronics Projects, LVP PIC low voltage progamming article
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A lot of people are but little used method of ball LVP “low voltage progamming” low voltage programming via RS232 serial port is used only 4 10k resistors. Computer program settings available in the IC Prog “programmer” to be chosen as the setting JDM I / O-Delay will be 3 level “interface” with the windows API ..
This is a very simple in-circuit-serial-programming (ICSP) solution for PICs capable of low-voltage-programming (LVP). All you need are some resistors. You can integrate these few parts directly into a 9pin (or 25pin) SUB-D connector housing, or you could think about integrating them into your final device where your PIC will have to go to work (for doing software updates when necessary).
For reading and writing program memory using this adapter, you also have to apply power to the PIC (+5V at Vdd) and tie MCLR to high level (Vdd) (Microchip suggests to use a resistor for MCLR because of latch-up risk). An oscillator circuit doesn’t have to be connected. Of course, connect the three lines PGD, PGC and PGM to this adapter, too.