During parallel programming, a 12V signal is connected to the Reset pin. It is therefore no internal protection diode from Reset to VCC; there is only one from GND to Reset. See the figure below.
To achieve the same protection on Reset as on other I/O pins, an external diode should be connected from Reset to VCC. A normal small-signal diode will do. In addition, a pull-up resistor (10kΩ typical) and a small filter capacitor (4.7nF) should be connected as shown in the figure below.
All this, of course, is not needed if Reset is connected directly to VCC, but then external reset and In-System Programming (ISP) is disabled, too.
If high ESD protection of Reset is not required, or is achieved by other components, the diode may be omitted. The resistor and capacitor are still recommended for optimum Reset behavior.
The diode must also be omitted if In-System Programming of devices like ATtiny11, which can only be programmed using 12V, is required. Then one of the ESD protection methods described earlier may be used instead.
