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14.8
Operation (SH7751R)
Operation specific to the SH7751R is described here. For details of operation, see section 14.3,
Operation.
14.8.1
Channel Specification for a Normal DMA Transfer
In normal DMA transfer mode, the DMAC always operates with eight channels, and external
requests are only accepted on channel 0 (
After setting the registers of the channels in use, including CHCR, SAR, DAR, and DMATCR,
DMA transfer is started on receiving a DMA transfer request in the transfer-enabled state (DE = 1,
DME = 1, TE = 0, NMIF = 0, AE = 0), in the order of predetermined priority. The transfer ends
when the transfer-end condition is satisfied. There are three modes for transfer requests: auto-
request, external request, and on-chip peripheral module request. The addressing modes for DMA
transfer are the single-address mode and the dual-address mode. Bus mode is selectable between
burst mode and cycle steal mode.
14.8.2
Channel Specification for DDT-Mode DMA Transfer
For DMA transfer in DDT mode, the DMAOR.DBL setting selects either four or eight channels.
External requests are accepted on channels 0–3 when DMAOR.DBL = 0, and on channels 0–7
when DMAOR.DBL = 1. For further information on these settings, see the entry on the DBL bit in
section 14.7.5, DMA Operation Register (DMAOR).
14.8.3
Transfer Channel Notification in DDT Mode
When the DMAC is set up for four-channel external request acceptance in DDT mode
(DMAOR.DBL = 0), the ID [1:0] bits are used to notify the external device of the DMAC channel
that is to be used. For more details, see section 14.5, On-Demand Transfer Mode (DDT Mode).
When the DMAC is set up for eight-channel external request acceptance in DDT mode
(DMAOR.DBL = 1), the ID [1:0] bits and the simultaneous (on the timing of
assertion of
from the
device of the DMAC channel that is to be used (see table 14.16, Notification of Transfer Channel
in Eight-Channel DDT Mode).
When the DMAC is set up for eight-channel external request acceptance in DDT mode
(DMAOR.DBL = 1), it is important to note that the
table 14.17.
Rev. 3.0, 04/02, page 562 of 1064
(bus-release notification) pin are used to notify the external
) and channel 1 (
pin has the two functions as shown in
).
assertion)
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