The maximum clock frequency is 12 MHz, but it can be overclocked up to 18 MHz with some limitations.
To use an external crystal, connect the crystal between pins 10 and 11, and set the OSCCFG register to select the external oscillator mode.
The minimum voltage required is 2.4V, but it's recommended to operate at 3.3V for optimal performance.
The UART module can be used by configuring the UART registers, setting the baud rate, and enabling the transmitter and receiver. Refer to the datasheet for specific register settings.
No, the P89LPC901FN,129 is not 5V tolerant, and operating it at 5V can damage the device. The recommended operating voltage is 3.3V.
P89LPC901FN,129 datasheet
by NXP Semiconductors
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