avr parallel programmer 5

The chief advantage of this programmer is its ability to protect both the target and the PC from odd voltages when one side is powered off. The buffers are open-drain, and each is pulled up to the Vcc of the receiving party. The MC74LCX07 has an operating Vcc rating of 2. 0 to 5. 5V. In addition, this programmer is the only buffered programmer that
avr parallel programmer 5 - schematic

allows the PC and the target to operate at different power supply voltages. Great for working with 3. 3V microprocessors on a 5V PC. The avrdude config entry is: Things to look out for are the values of series resistors R1 and R4. If the pullup resistor on the reset line of the microcontroller is of a low enough value, the reset line may not go low enough when pulled low by the programmer. The same is true for the MISO line on the PC side. R4 is pulling down against a pullup, and the voltage at the port pin must be low enough to make a logic "0" when pulled by the programmer. This one was very difficult for me to build, due to the SO14 package, but I think it is my programmer of choice for AVR`s. It is as fast as the other parallel programmers, safer than any, and so far, 100% reliable. Perhaps I`ll do a circuit board and rebuild this one (and not try to cram it into a headshell).

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