How a LPC 2368 controller get the bus mastership on 68K address and data bus
The 68000 seems to have been designed for use in multicontroller environments, where other controllers, like another microcontroller or a DMA controller need to assume bus control.  

The 68000 uses 3 control lines for this:  


BR (Bus Request), active low, input. This is used by the LPC2368 to signal that it want to control the bus.  
BG (Bus Grant), active low, output. The 68000 will pull this pin low to indicate it will release the bus when the current cycle completes.  
BGACK (Bus Grant Acknowledge), active low, input. The LPC2368 will make this pin low when it's ready to take control. BG has to be low, and AS (Address Strobe, active low) high.


The LPC2368 releases control of the bus by making BR high again. After completing its current cycle it then releases BGACK, and the 68000 has control again.  

(source)

(thanks to supercat for the hint)