The maximum clock frequency for the P89LPC921FDH,512 is 12 MHz, but it can be overclocked up to 18 MHz with some limitations.
The oscillator can be configured using the OSCCFG register. The oscillator frequency can be set to either 12 MHz or 18 MHz, and the oscillator mode can be set to either internal or external.
The maximum current consumption of the P89LPC921FDH,512 is approximately 10 mA at 3.3V and 12 MHz frequency.
The UART interface on the P89LPC921FDH,512 can be used by configuring the UART registers and using the UART interrupts. The UART baud rate can be set using the UARTBSEL and UARTBREG registers.
No, the P89LPC921FDH,512 is designed to operate at 3.3V and should not be used with a 5V power supply. Using a 5V power supply can damage the device.
P89LPC921FDH,512 datasheet
by NXP Semiconductors
