Marketing speech:

The LPC915 / LPC916 / LPC917 can be used as a companion chip for higher performance CPUs. The functions performed range from external EEPROM, power control device, low precision analog sensor, based on multiple serial communication options. The most interesting point is the minimal external requirements for the LPC900 devices. The IRC is accurate enough to be used for serial communications UART, SPI or I2C? . With 2k Flash, there is enough memory to combine a serial interface with a 1 KB EEPROM.

What does it do

We have a generic MCU on our board, and we don't know what's in it. Browsing through the source we can see however that we communicate with it using I2C? . The MCU has address 0x28, and can communicate with an i2c clock of at most 10000 (bps?).

i2c	type	data	does
0xD9	R8B?		Read battery charge register?
0xDB	R8B?		Get battery status
0xD8	W8B?	1	Shutdown power

IRQ's are generated on GPIO 65. If somebody hits the power switch, an IRQ should be generated.