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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)
8.5
Interrupt Sources
EXDMAC interrupt sources are a transfer end indicated by the transfer counter, and repeat area
overflow interrupts. Table 8.4 shows the interrupt sources and their priority order.
Table 8.4
Interrupt Sources and Priority Order
Interrupt
Interrupt source
Interrupt Priority
EXDMTEND2
Transfer end indicated by channel 2 transfer counter
Channel 2 source address repeat area overflow
Channel 2 destination address repeat area overflow
High
EXDMTEND3
Transfer end indicated by channel 3 transfer counter
Channel 3 source address repeat area overflow
Channel 3 destination address repeat area overflow
Low
Summary of Contents for H8S/2376 F-ZTAT
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