Summary of Microchip PIC Programmer ICSP Circuit Requirements
Kanda provides a recommended ICSP circuit for PIC programmers that protects target circuits and improves programming reliability. Key recommendations: use a VDD protection diode (or series resistor) if programmer voltage exceeds target; fit a pull-up resistor on MCLR/VPP (1K–10K, 4K7 minimum for specific PIC16F families); limit MCLR cap to 10K series resistors or a multiplexer; include decoupling on PIC18F J core Vcc.
Parts used in the Kanda ICSP PIC Programmer Circuit:
- Programmer capable of 3.3V or 5V VDD and VPP (Kanda handheld or similar)
- Diode on VDD (Schottky suggested)
- Series resistor (alternative to diode in some cases)
- MCLR/VPP pull-up resistor (1K minimum, 10K recommended, 4K7 for some PIC16F)
- 100nF capacitor on MCLR/VPP (optional; smaller recommended; omit for LVP)
- Series resistors on PGC and PGD (greater than 10K if isolating application circuitry)
- 4053 analog multiplexer or similar (for exceptional isolation cases)
- PGM line and associated resistor (required for Low Voltage Programming)
- Decoupling capacitor for PIC18F J VccCore to Ground (typically 100nF)
Microchip do not recommend any particular circuit for ICSP programming. There are diagrams for different tools, such as Pro Mate and PICKit2 with similar circuitry but slight variations. In some schematics, their suggested resistor values are too small, in our opinion, and can cause problems with programmers, even Microchip ones.
Microchip PIC Programmer ICSP Circuit
Kanda have developed a recommended In System Programming circuit that will work effectively with our PIC programmer range, and other PIC programmers. This circuit is shown in the diagram below. Please read the notes that describe the circuit and explain the effect of extra components such as capacitors. 
Notes on PIC ICSP Circuit
- Kanda programmers are designed to provide 3.3V or 5V to the target circuit, but some other ICSP programmers always supply 5V. If your circuit operates at a lower voltage than the programmer, then the diode shown on VDD should be fitted to protect the rest of the circuit. A series resistor may be acceptable instead of the diode in some cases.
The maximum current that the programmer can supply is often limited, so you should fit the diode on VDD if the programmer over-current circuit trips. - MCLR/VPP pin needs a resistor to VDD. A minimum of 1K should work but 10K is better. PIC16F devices with only VDD first ICSP entry (PIC16F8x/87x/7x/7×7) should be fitted with a 4K7 resistor as a minimum to reduce the possibility of code running before VPP rises. Supervisory circuits or push buttons on MCLR should be isolated from the VPP voltage, by placing them on the VDD side of the resistor or by fitting a Schottky diode on this line as per note 1.
- The 100nF capacitor shown on MCLR/VPP pin is optional for HVP but we do recommend that a capacitor is fitted to avoid glitches on MCLR. 100nF is the maximum value, and we recommend something smaller. Larger capacitors may prevent the PIC from entering HVP mode. Do not fit for LVP mode.
- If possible, Clock and Data lines should be dedicated to ICSP but where this is not possible, the application circuit should be isolated from the data and clock lines with series resistors, above 10K. This is especially important if either of these lines forces the pin as an input or output. In exceptional cases, series resistors may not be sufficient and a 4053 multiplexer or similar circuit should be used.
Capacitors on these programming lines should be avoided if at all possible. If they are needed, for noise immunity for example, then the maximum capacitance that all programmers can handle is 1nF, although some are better. - If LVP mode is used, this resistor must be fitted.
- The PGM line is only needed for Low Voltage Programming – LVP mode.
- PIC18F J parts need a decoupling capacitor between VccCore pin and Ground, typically 100nF.
Notes on PIC ICSP Circuit
- Kanda programmers are designed to provide 3.3V or 5V to the target circuit, but some other ICSP programmers always supply 5V. If your circuit operates at a lower voltage than the programmer, then the diode shown on VDD should be fitted to protect the rest of the circuit. A series resistor may be acceptable instead of the diode in some cases.
The maximum current that the programmer can supply is often limited, so you should fit the diode on VDD if the programmer over-current circuit trips. - MCLR/VPP pin needs a resistor to VDD. A minimum of 1K should work but 10K is better. PIC16F devices with only VDD first ICSP entry (PIC16F8x/87x/7x/7×7) should be fitted with a 4K7 resistor as a minimum to reduce the possibility of code running before VPP rises. Supervisory circuits or push buttons on MCLR should be isolated from the VPP voltage, by placing them on the VDD side of the resistor or by fitting a Schottky diode on this line as per note 1.
- The 100nF capacitor shown on MCLR/VPP pin is optional for HVP but we do recommend that a capacitor is fitted to avoid glitches on MCLR. 100nF is the maximum value, and we recommend something smaller. Larger capacitors may prevent the PIC from entering HVP mode. Do not fit for LVP mode.
- If possible, Clock and Data lines should be dedicated to ICSP but where this is not possible, the application circuit should be isolated from the data and clock lines with series resistors, above 10K. This is especially important if either of these lines forces the pin as an input or output. In exceptional cases, series resistors may not be sufficient and a 4053 multiplexer or similar circuit should be used.
Capacitors on these programming lines should be avoided if at all possible. If they are needed, for noise immunity for example, then the maximum capacitance that all programmers can handle is 1nF, although some are better. - If LVP mode is used, this resistor must be fitted.
- The PGM line is only needed for Low Voltage Programming – LVP mode.
- PIC18F J parts need a decoupling capacitor between VccCore pin and Ground, typically 100nF.
Kanda ICSP PIC Programmers
Kanda ICSP PIC ProgrammersKanda Handheld PIC Programmers will provide 3.3V or 5V VDD to target PIC microcontroller circuits. The target circuit can be powered or unpowered. This can be user selected for most PIC microcontrollers but it is fixed to 3.3V for J type PIC microcontrollers and LF parts that can be damaged by 5V. The high Voltage programming voltage (VPP) is set to 12V for most PIC devices but is automatically set to 9V for PIC18F K type and newest PIC16F PIC microcontrollers
For more detail: Microchip PIC Programmer ICSP Circuit Requirements
- Do I need a diode on VDD when using a programmer?
Fit the diode if your circuit operates at a lower voltage than the programmer or if the programmer over-current circuit trips; a series resistor may be acceptable in some cases. - What value resistor should be used on MCLR/VPP?
Use at least 1K, 10K is better; for PIC16F devices with only VDD first ICSP entry use 4K7 minimum. - Is a capacitor recommended on MCLR/VPP?
A capacitor up to 100nF is optional for HVP to avoid glitches; smaller is recommended and do not fit for LVP. - Can I have capacitors on PGC and PGD programming lines?
Avoid capacitors; if needed for noise immunity keep total capacitance to 1nF maximum. - How should I isolate application circuitry on Clock and Data lines?
Use series resistors above 10K, or use a 4053 multiplexer or similar if resistors are insufficient. - When is the PGM line required?
The PGM line is only needed for Low Voltage Programming (LVP) mode. - Do Kanda programmers supply target VDD?
Kanda programmers can provide 3.3V or 5V VDD; for J type and some LF parts they provide fixed 3.3V. - What VPP voltage do Kanda programmers use?
VPP is set to 12V for most PICs and automatically to 9V for PIC18F K type and newest PIC16F microcontrollers. - Is decoupling required for PIC18F J parts?
Yes; fit a decoupling capacitor between VccCore and Ground, typically 100nF.
