Rev. 1.0, 09/01, page 344 of 904
In block transfer mode, the upper 8 bits are never updated, so there is no problem with using word
access.
Do not write to EDTCR for a channel on which a transfer operation is in progress. If there is
contention between an address update associated with DMA transfer and a write by the CPU, the
CPU write has priority.
In the event of contention between an EDTCR update from 1 to 0 and a write (of a nonzero value)
by the CPU, the CPU write value has priority as the EDTCR value, but transfer is terminated.
Transfer does not end if the CPU writes 0 to EDTCR.
Figure 8.11 shows EDTCR update operations in normal transfer mode and block transfer mode.
23
0
0
EDTCR
Fixed
23
0
0
Before update
After update
23
0
1 to H'FFFFFF
EDTCR
–1
23
0
0 to H'FFFFFE
EDTCR
EDTCR in normal transfer mode
EDTCR in block transfer mode
Fixed
Before update
After update
23
15
0
16
1 to H'FFFF
Block
size
EDTCR
–1
23
15
0
16
0
Block
size
23
15
0
16
0 to H'FFFE
Block
size
23
15
0
16
0
Block
size
Figure 8.11 EDTCR Update Operations in Normal Transfer Mode and
Block Transfer Mode
EDA Bit in EDMDR: The EDA bit in EDMDR is written to by the CPU to control enabling and
disabling of data transfer, but may be cleared automatically by the EXDMAC due to the DMA
transfer status. There are also periods during transfer when a 0-write to the EDA bit by the CPU is
not immediately effective.
Conditions for EDA bit clearing by the EXDMAC include the following:
•
When the EDTCR value changes from 1 to 0, and transfer ends
•
When a repeat area overflow interrupt is requested, and transfer ends
Содержание H8S/2376 F-ZTAT
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