I have a 16f88 programmer (of my own design) that was working quite well until recently. For some reason now, the MCU just decided to stop responding. By this I mean, when I enter into "read data" mode and pulse the clock, nothing happens on the data pin.
My programming circuit is very simple: two pins from the parallel port go into an inverter. The inverted signal goes to RB6 and RB7 of the 16f88 (the clock and data pins during programming mode). A third pin goes to a transistor that switches on the 12V source (for the MCLR pin on the 16f88). All three pins are controlled by a c++ program I wrote. I also have a 4th pin of the parallel port connected through the inverter to RB7. This pin is for reading the bits of memory when in "read data" mode.
Like I said, this setup was working great before. I was able to program a hex file into the chip and have it read the memory values back to me. Now that it's stopped working, I've worn my multimeter probes thin doing voltage and continuity checks. I even slowed the program way down and put LEDs on RB6 and RB7 to watch the 0's and 1's going into the chip. The circuit seems to be doing exactly what it's supposed to. I've ruled out the parallel port pins of being faulty. And all of my voltages look good (5V circuit power, ~4.5V on all the pins on the parallel port, ~4.5V signals from the inverter, 12V for the MCLR pin). The breadboard does not seem to be at fault either.
I have two 16f88's and I've tried both in the circuit. Still, I cannot rule out that I've managed to fry both of them. Is there a quick method to determine whether the chips are even alive anymore? Any other troubleshooting ideas?
Thanks in advance!
-Dan
My programming circuit is very simple: two pins from the parallel port go into an inverter. The inverted signal goes to RB6 and RB7 of the 16f88 (the clock and data pins during programming mode). A third pin goes to a transistor that switches on the 12V source (for the MCLR pin on the 16f88). All three pins are controlled by a c++ program I wrote. I also have a 4th pin of the parallel port connected through the inverter to RB7. This pin is for reading the bits of memory when in "read data" mode.
Like I said, this setup was working great before. I was able to program a hex file into the chip and have it read the memory values back to me. Now that it's stopped working, I've worn my multimeter probes thin doing voltage and continuity checks. I even slowed the program way down and put LEDs on RB6 and RB7 to watch the 0's and 1's going into the chip. The circuit seems to be doing exactly what it's supposed to. I've ruled out the parallel port pins of being faulty. And all of my voltages look good (5V circuit power, ~4.5V on all the pins on the parallel port, ~4.5V signals from the inverter, 12V for the MCLR pin). The breadboard does not seem to be at fault either.
I have two 16f88's and I've tried both in the circuit. Still, I cannot rule out that I've managed to fry both of them. Is there a quick method to determine whether the chips are even alive anymore? Any other troubleshooting ideas?
Thanks in advance!
-Dan