Datasheet

Section 8 EXDMA Controller (EXDMAC)
Page 434 of 1408 R01UH0309EJ0500 Rev. 5.00
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
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.
The source address repeat area is specified by bits SARA4 to SARA0 in EDACR, and the
destination address repeat area by bits DARA4 to DARA0 in EDACR. The size of each repeat
area can be specified independently.
When the address register value is the last address in the repeat area and repeat area overflow
occurs, EXDMA transfer can be temporarily halted and an interrupt request sent to the CPU. If the
SARIE bit in EDACR is set to 1, when the source address register overflows the repeat area, the
IRF bit is set to 1 and the EDA bit cleared to 0 in EDMDR, and transfer is terminated. If EDIE = 1
in EDMDR, an interrupt is requested. If the DARIE bit in EDACR is set to 1, the above applies to
the destination address register.
If the EDA bit in EDMDR is set to 1 during interrupt generation, transfer is resumed. Figure 8.9
illustrates the operation of the repeat area function.