i need clarity on a pic 16f877

[ZIGGY_DAN]

I have built a pic programmer and am new to the world of pic, my programmer does respond to signals from the parallel port and i use nigels software. the issue that i am having is that it doesnt seem to write to the pic, when i try to verify the code i get a verify error at address 0x0000 or something to that effect. The voltage i am applying to MCLR is 13.4V and i am using a 4MHZ oscillator on a pic16f877, what do i need to do to the other pins, i have data to RB7 and clock to rb6, i read somewhere that i need to pull RB5 to 5V and somewhere else i read that i need to pull RB3 to 0V.

 

[ClydeCrashKop]

You might make sure the program is using the right address for LPT1 and that the hardware settings are right.

 

[eblc1388]

Just a couple of suggestions.

1. You don't need a crystal connected to F877 while in programming. You can try removing it to see if programming is successful.

2. You should be using voltage regulators for the 13V Vpp and 5V Vdd against ripples in power supply.

3. RB5 can be left unconnected and connect resistor of lower than 10Khm: from RB3 to 0V. A 10Khm: resistor connects to MCLR pin & 0V sometimes helps too.

4. Without a PIC in the socket, perform a hardware check using the "Options" menu inside the WinPicProg. Place voltmeter on MCLR, PGD or PGC pin to see you can actually change their voltage level using the "ON/OFF" click button at the bottom of the software. This would prove that correct communication exists between your programmer and the PC.

5. Try a READ operation without a PIC. You should get back 0x3FFF or there is something wrong with the signaling or polarity of the signal.

 

[ZIGGY_DAN]

The program is definitely using the correct adress, i use a L7805 for the 5V to the PIC and a L7812(using two diodes to raise the potential of ground for the reference pin to get 13.4V) i have a 1K resistor from MCLR to ground and when i try to read the pic without anything in the socket i do get 0x3FFF. I will try a hardware check from the options in win pic prog and i will add a 4K7 resistor from RB3 to ground. thanks for the replies