HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 458

• 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)
IRF Bit in EDMDR: The IRF bit in EDMDR is set to 1 when an interrupt request source occurs.
If the EDIE bit in EDMDR is 1 at this time, an interrupt is requested.
The timing for setting the IRF bit to 1 is when the EDA bit in EDMDR is cleared to 0 and transfer
ends following the end of the DMA transfer bus cycle in which the source generating the interrupt
occurred.
If the EDA bit is set to 1 and transfer is resumed during interrupt handling, the IRF bit is
automatically cleared to 0 and the interrupt request is cleared.
For details on interrupts, see section 8.5, Interrupt Sources.
8.4.8
The priority order of the EXDMAC channels is: channel 2 > channel 3. Table 8.3 shows the
EXDMAC channel priority order.
Table 8.3
Channel
Channel 2
Channel 3
If transfer requests occur simultaneously for a number of channels, the highest-priority channel
according to the priority order in table 8.3 is selected for transfer.
Transfer Requests from Multiple Channels (Except Auto Request Cycle Steal Mode): If
transfer requests for different channels are issued during a transfer operation, the highest-priority
channel (excluding the currently transferring channel) is selected. The selected channel begins
transfer after the currently transferring channel releases the bus. If there is a bus request from a bus
master other than the EXDMAC at this time, a cycle for the other bus master is initiated. If there is
no other bus request, the bus is released for one cycle.
Channel switching does not take place during a burst transfer or a block transfer of a single block.
Figure 8.13 shows a case in which transfer requests for channels 2 and 3 are issued
simultaneously. The example shown in the figure illustrates the handling of external requests in
the cycle steal mode.
Rev.7.00 Mar. 18, 2009 page 390 of 1136
REJ09B0109-0700
Channel Priority Order
EXDMAC Channel Priority Order
Priority
High
Low