Section 14 Direct Memory Access Controller (DMAC)
Rev. 1.00 Oct. 01, 2007 Page 591 of 1956
REJ09B0256-0100
14.4 Operation
When there is a DMA transfer request, the DMAC starts the transfer according to the
predetermined channel priority; 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.
14.4.1
DMA Transfer Requests
DMA transfer requests are basically generated in either the data transfer source or destination, but
they can also be generated by external devices or on-chip peripheral modules that are neither the
source nor the destination. Transfers can be requested in three modes: auto request, external
request, and on-chip peripheral module request. The request mode is selected in the bits RS[3:0] in
CHCR0 to CHCR5, and DMARS0 to DMARS2.
(1) Auto-Request
Mode
When there is no transfer request signal from an external source, as in a memory-to-memory
transfer or a transfer between memory and an on-chip peripheral module unable to request a
transfer, auto-request mode allows the DMAC to automatically generate a transfer request signal
internally. When the DE bits in CHCR0 to CHCR5 and the DME bit in DMAOR are set to 1, the
transfer begins so long as the AE and NMIF bits in DMAOR are all 0.
(2) External Request Mode
In this mode, a transfer is performed at the request signal (
DREQ0
to
DREQ3
) of an external
device. This mode is valid only in channel 0 to 3. In this mode, the RS[3:0] bits in CHCRn (n = 0
to 3) should be B'0000. When this mode is selected, if the DMA transfer is enabled (DE = 1, DME
= 1, TE = 0, AE = 0, NMIF = 0), a transfer is performed upon a request at the DREQ input.
Table 14.5 Setting External Request Mode with RS bit
CHCR
RS[3] RS[2] RS[1] RS[0] Address
Mode
Transfer Source
Transfer Destination
0 0 0 0 Dual
Address
Mode
Any
Any
Choose to detect
DREQ
by either the edge or level of the signal input with the DL bit and DS bit
in CHCRn (n = 0 to 3) as shown in table 14.6. The source of the transfer request does not have to
be the data transfer source or destination.
Содержание SH7763
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Страница 630: ...Section 13 PCI Controller PCIC Rev 1 00 Oct 01 2007 Page 564 of 1956 REJ09B0256 0100 ...
Страница 686: ...Section 14 Direct Memory Access Controller DMAC Rev 1 00 Oct 01 2007 Page 620 of 1956 REJ09B0256 0100 ...
Страница 710: ...Section 16 Clock Pulse Generator CPG Rev 1 00 Oct 01 2007 Page 644 of 1956 REJ09B0256 0100 ...
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Страница 1350: ...Section 30 SIM Card Module SIM Rev 1 00 Oct 01 2007 Page 1284 of 1956 REJ09B0256 0100 ...
Страница 1484: ...Section 33 Audio Codec Interface HAC Rev 1 00 Oct 01 2007 Page 1418 of 1956 REJ09B0256 0100 ...
Страница 1560: ...Section 35 USB Host Controller USBH Rev 1 00 Oct 01 2007 Page 1494 of 1956 REJ09B0256 0100 ...
Страница 1720: ...Section 37 LCD Controller LCDC Rev 1 00 Oct 01 2007 Page 1654 of 1956 REJ09B0256 0100 ...
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