SH7280 Datasheet, PDF (439/1726 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine family

Section 10 Direct Memory Access Controller (DMAC)
10.4 Operation
When there is a DMA transfer request, the DMAC starts the transfer according to the
predetermined channel priority order; when the transfer end conditions are satisfied, it ends the
transfer. Transfers can be requested in three modes: auto request, external request, and on-chip
peripheral module request. In bus mode, burst mode or cycle steal mode can be selected.
10.4.1 Transfer Flow
After the DMA source address registers (SAR), DMA destination address registers (DAR), DMA
transfer count registers (DMATCR), DMA channel control registers (CHCR), DMA operation
register (DMAOR), and DMA extension resource selector (DMARS) are set for the target transfer
conditions, the DMAC transfers data according to the following procedure:
1. Checks to see if transfer is enabled (DE = 1, DME = 1, TE = 0, AE = 0, NMIF = 0)
2. When a transfer request comes and transfer is enabled, the DMAC transfers one transfer unit of
data (depending on the TS0 and TS1 settings). For an auto request, the transfer begins
automatically when the DE bit and DME bit are set to 1. The DMATCR value will be
decremented by 1 for each transfer. The actual transfer flows vary by address mode and bus
mode.
3. When half of the specified transfer count is exceeded (when DMATCR reaches half of the
initial value), an HEI interrupt is sent to the CPU if the HIE bit in CHCR is set to 1.
4. When transfer has been completed for the specified count (when DMATCR reaches 0), the
transfer ends normally. If the IE bit in CHCR is set to 1 at this time, a DEI interrupt is sent to
the CPU.
5. When an address error in the DMAC or an NMI interrupt is generated, the transfer is
terminated. Transfers are also terminated when the DE bit in CHCR or the DME bit in
DMAOR is cleared to 0.
Figure 10.2 is a flowchart of this procedure.
Rev. 1.00 Jun. 26, 2008 Page 409 of 1692
REJ09B0393-0100