Hello!
I just started a class in microcontrollers. I was following the lab book at home and had a PIC 16F877A on my breadboard. I had programmed it to blink an LED with in-circuit programming, and that was working. I left that running for hours and it worked fine. Then I realized I had never tried the RESET button.
The !MCLR line, pin 1, is tied to +5V with a 10k resistor, and a switch connects it to ground.
I pressed the Reset button a few times. The LED stopped blinking, the button got HOT while I pressed it, and the PIC also got hot!
Now the chip does not function. I have not tried to re-program it in case it could cause damage to the programmer (is this possible?).
It seems to me that when I pressed the Reset button, which connects !MCLR/pin 1 to ground, that a lot of current flowed through the switch, causing it to heat up. This current flow damaged the PIC. But why did it happen?
I have looked in the datasheet and I see that they say the following:
So in summary, I don't know what I did! Any advice?
I just started a class in microcontrollers. I was following the lab book at home and had a PIC 16F877A on my breadboard. I had programmed it to blink an LED with in-circuit programming, and that was working. I left that running for hours and it worked fine. Then I realized I had never tried the RESET button.
The !MCLR line, pin 1, is tied to +5V with a 10k resistor, and a switch connects it to ground.
I pressed the Reset button a few times. The LED stopped blinking, the button got HOT while I pressed it, and the PIC also got hot!
Now the chip does not function. I have not tried to re-program it in case it could cause damage to the programmer (is this possible?).
It seems to me that when I pressed the Reset button, which connects !MCLR/pin 1 to ground, that a lot of current flowed through the switch, causing it to heat up. This current flow damaged the PIC. But why did it happen?
I have looked in the datasheet and I see that they say the following:
My school's text doesn't use the capacitor, but MCLR is also not tied directly to VDD, but through a resistor. Also, the datasheet does not mention using a button to reset.The behavior of the ESD protection on the MCLR pin
differs from previous devices of this family. Voltages
applied to the pin that exceed its specification can
result in both Resets and current consumption outside
of device specification during the Reset event. For this
reason, Microchip recommends that the MCLR pin no
longer be tied directly to VDD. The use of an RCR
network, as shown in Figure 14-5, is suggested.
So in summary, I don't know what I did! Any advice?