r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 332

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 6 Bus Controller (BSC)
(4)
The EXDMAC sends the bus arbiter a request for the bus when an activation request is generated.
As the EXDMAC is used exclusively for transfers to and from the external bus, if the bus is
transferred to the EXDMAC, internal accesses by other internal bus masters are still executed in
parallel.
In normal transfer mode or cycle steal transfer mode, the EXDMAC releases the bus after a single
transfer.
In block transfer mode, it releases the bus after transfer of one block, and in burst transfer mode,
after completion of the transfer. By setting the BGUP bit to 1 in EDMDR, it is possible to specify
temporary release of the bus in the event of an external access request from an internal bus master.
For details see section 8, EXDMA Controller (EXDMAC).
Note: The EXDMAC is not supported by the H8S/2424 Group.
(5)
When the BREQ pin goes low and an external bus release request is issued while the BRLE bit is
set to 1 in BCR, a bus request is sent to the bus arbiter.
External bus release can be performed on completion of an external bus cycle.
6.14
In a reset, this LSI, including the bus controller, enters the reset state immediately, and any
executing bus cycle is aborted.
Rev. 1.00 Sep. 19, 2008 Page 304 of 1270
REJ09B0466-0100
EXDMAC
External Bus Release
Bus Controller Operation in Reset