Datasheet

Section 6 Bus Controller
Rev. 4.00 Sep 27, 2006 page 177 of 1130
REJ09B0327-0400
6.7 Bus Arbitration
6.7.1 Overview
This LSI have a bus arbiter that arbitrates bus master operations.
There are two bus masters, the CPU and the DTC, which perform read/write operations when they
have possession of the bus. Each bus master requests the bus by means of a bus request signal. The
bus arbiter determines priorities at the prescribed timing, and permits use of the bus by means of a
bus request acknowledge signal. The selected bus master then takes possession of the bus and
begins its operation.
6.7.2 Operation
The bus arbiter detects the bus masters’ bus request signals, and if the bus is requested, sends a bus
request acknowledge signal to the bus master making the request. If there are bus requests from
both bus masters, the bus request acknowledge signal is sent to the one with the higher priority.
When a bus master receives the bus request acknowledge signal, it takes possession of the bus
until that signal is canceled.
The order of priority of the bus masters is as follows:
(High) DTC > CPU (Low)