r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 443

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

(2)
In burst mode, once the EXDMAC acquires the bus it continues transferring data, without
releasing the bus, until the transfer end condition is satisfied. There is no burst mode in external
request mode.
In burst mode, once transfer is started it is not interrupted even if there is a transfer request from
another channel with higher priority. When the burst mode channel finishes its transfer, it releases
the bus in the next cycle in the same way as in cycle steal mode.
When the EDA bit is cleared to 0 in EDMDR, DMA transfer is halted. However, DMA transfer is
executed for all transfer requests generated within the EXDMAC up until the EDA bit was cleared
to 0.
If a repeat area overflow interrupt is generated, the EDA bit is cleared to 0 and transfer is
terminated.
When the BGUP bit is set to 1 in EDMDR, the bus is released if a bus request is issued by another
bus master during burst transfer. If there is no bus request, burst transfer is executed even if the
BGUP bit is set to 1.
Figure 8.6 shows examples of the timing in burst mode.
Burst Mode
Bus cycle
Bus cycle
Transfer conditions:
Transfer conditions:
Auto request mode, BGUP = 0
Auto request mode, BGUP = 1
CPU
CPU
Figure 8.6 Examples of Timing in Burst Mode
EXDMAC
CPU
EXDMAC
EXDMAC operates alternately with CPU
CPU
EXDMAC
EXDMAC
CPU cycle not generated
Rev. 1.00 Sep. 19, 2008 Page 413 of 1342
Section 8 EXDMA Controller (EXDMAC)
EXDMAC
CPU
EXDMAC
CPU
REJ09B0467-0100
CPU
CPU