HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 456

• 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)
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
• When an NMI interrupt is generated, and transfer halts
• A reset
• Hardware standby mode
• When 0 is written to the EDA bit, and transfer halts
When transfer is halted by writing 0 to the EDA bit, the EDA bit remains at 1 during the DMA
transfer period. In block transfer mode, since a block-size transfer is carried out without
interruption, the EDA bit remains at 1 from the time 0 is written to it until the end of the current
block-size transfer.
Rev.7.00 Mar. 18, 2009 page 388 of 1136
REJ09B0109-0700
EDTCR in normal transfer mode
EDTCR
EDTCR
EDTCR in block transfer mode
EDTCR
EDTCR
Figure 8.11 EDTCR Update Operations in Normal Transfer Mode and
23
23
23
23
Block
Block
size
size
16
16
1 to H'FFFFFF
Before update
Before update
15
15
0
1 to H'FFFF
Block Transfer Mode
0
0
0
0
0
Fixed
Fixed
–1
–1
23
23
23
23
Block
Block
size
size
16
16
0 to H'FFFFFE
After update
After update
15
15
0
0 to H'FFFE
0
0
0
0
0