Отправлено BLACKEAGLE 09 марта 2002 г. 15:13

Исчерпывающий (имхо) ответ на днях появился в Cygnal'овской конфе. Речь там шла об F3xx, но справедливо это и для остальных C8051Fxxx:

All of the port pins on the 'F300 are 5-volt tolerant. That means that you can apply up to 5.8V without causing device damage. This applies even if the ADC or comparators are configured to measure the pin. However, it is not possible to actually measure signals much greater than VDD because the "5-volt tolerant" circuitry actually disconnects the interior device circuitry (ADC, comparators, port I/O logic) from the exterior pin when the voltage gets a few hundred millivolts above VDD.

Regardless, it may be prudent to place a modest series resistor (100 ohms or so) in the path between the 5V device and the port pin input to limit potential power-up transient currents between the devices.

• Ссылка на Cygnal'овские конференции — BLACKEAGLE   (09.03.2002 15:24, пустое, ссылка)