Datasheet

Section 8 EXDMA Controller
Rev. 3.00 Mar 17, 2006 page 359 of 926
REJ09B0283-0300
Caution is required when setting the repeat area overflow interrupt of the repeat area function in
block transfer mode. See section 8.4.6, Repeat Area Function, for details.
Block transfer is aborted if an NMI interrupt is generated. See section 8.4.12, Ending DMA
Transfer, for details.
Figure 8.8 shows an example of DMA transfer timing in block transfer mode.
CPUCPU CPU EXDMAC EXDMAC EXDMAC CPU
Bus cycle
EDRAK
ETEND
EDREQ
CPU cycle not generated
One-block transfer cycle
Transfer conditions:
• Single address mode
• BGUP = 0
• Block size (EDTCR[23:16]) = 3
Figure 8.8 Example of Timing in Block Transfer Mode
8.4.6 Repeat Area Function
The EXDMAC has a function for designating a repeat area for source addresses and/or destination
addresses. When a repeat area is designated, the address register values repeat within the range
specified as the repeat area. Normally, when a ring buffer is involved in a transfer, an operation is
required to restore the address register value to the buffer start address each time the address
register value is the last address in the buffer (i.e. when ring buffer address overflow occurs), but if
the repeat area function is used, the operation that restores the address register value to the buffer
start address is performed automatically within the EXDMAC.
The repeat area function can be set independently for the source address register and the
destination address register.