HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 487

• Manufacturer Part Number: HD6412373R
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 8 EXDMA Controller (EXDMAC)
In block transfer mode, operation is aborted even in the middle of a block-size transfer. As the
transfer is halted midway through a block, the BEF bit in EDMDR is set to 1 to indicate that the
block transfer was not carried out normally.
When transfer is aborted, register values are retained, and as the address registers indicate the next
transfer addresses, transfer can be resumed by setting the EDA bit to 1 in EDMDR. If the BEF bit
is 1 in EDMDR, transfer can be resumed from midway through a block.
Hardware Standby Mode and Reset Input: The EXDMAC is initialized in hardware standby
mode and by a reset. DMA transfer is not guaranteed in these cases.
8.4.13
Relationship between EXDMAC and Other Bus Masters
The read and write operations in a DMA transfer cycle are indivisible, and a refresh cycle, external
bus release cycle, or internal bus master (CPU, DTC, or DMAC) external space access cycle never
occurs between the two.
When read and write cycles occur consecutively, as in burst transfer or block transfer, a refresh or
external bus release state may be inserted after the write cycle. As the internal bus masters are of
lower priority than the EXDMAC, external space accesses by internal bus masters are not
executed until the EXDMAC releases the bus.
The EXDMAC releases the bus in the following cases:
1. When DMA transfer is performed in cycle steal mode
2. When switching to a different channel
3. When transfer ends in burst transfer mode
4. When transfer of one block ends in block transfer mode
5. When burst transfer or block transfer is performed with the BGUP bit in EDMDR set to 1
(however, the bus is not released between read and write cycles)
Rev.7.00 Mar. 18, 2009 page 419 of 1136
REJ09B0109-0700