HD6412332 RENESAS [Renesas Technology Corp], HD6412332 Datasheet - Page 227

• Manufacturer Part Number: HD6412332
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

6.10.5
If MSTPCR is set to H'FFFF or H'EFFF and a transition is made to sleep mode, the external bus
release function will halt. Therefore, these settings should not be used.
6.11
6.11.1
The chip has a bus arbiter that arbitrates bus master operations.
There are three bus masters, the CPU, DTC, and DMAC, 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.
6.11.2
The bus arbiter monitors 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 more than one bus master, the bus request acknowledge signal is sent to the one with the
highest 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:
An external access by an internal bus master, external bus release, and a refresh can be executed in
parallel.
If an external bus release request, a refresh request, and an external access by an internal bus
master occur simultaneously, the order of priority is as follows:
As a refresh and an external access by an internal bus master can be executed simultaneously,
there is no relative order of priority for these two operations.
(High) DMAC > DTC > CPU (Low)
(High) Refresh > External bus release (Low)
(High) External bus release > Internal bus master external access (Low)
Usage Note
Bus Arbitration
Overview
Operation
Rev.4.00 Sep. 07, 2007 Page 197 of 1210
REJ09B0245-0400