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Section 13 Direct Memory Access Controller (DMAC)
Rev. 4.00 Sep. 14, 2005 Page 426 of 982
REJ09B0023-0400
13.4.2
DMA Transfer Requests
DMA transfer requests are basically generated in either the data transfer source or destination, but
they can also be generated by devices and 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 module request. The request mode is selected in the RS3 to RS0 bits of the DMA channel
control registers 0 to 3 (CHCR_0 to CHCR_3), and the DMA extension resource selectors 0 and 1
(DMARS0, DMARS1).
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, the auto-request mode allows the DMAC to automatically generate a
transfer request signal internally. When the DE bits of CHCR_0 to CHCR_3 and the DME bit of
the DMAOR are set to 1, the transfer begins so long as the TE bits of CHCR_0 to CHCR_3 and
the NMIF bit of DMAOR are all 0.
External Request Mode: In this mode a transfer is performed at the request signals (
DREQ0
to
DREQ1
) of an external device. This is valid for DMA channels 0 to 1. Choose one of the modes
shown in table 13.4 according to the application system. 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 13.4 Selecting External Request Modes with the RS Bits
RS3 RS2 RS1 RS0 Address
Mode
Source
Destination
0 0 0 0 Dual
address
mode
Any
Any
0 External
memory,
memory-mapped
external device
External device with
DACK
0 0 1
1
Single address mode
External device with
DACK
External memory,
memory-mapped
external device
Choose to detect
DREQ
by either the falling edge or low level of the signal input with the
DREQ
level (DL) bit and DS bit of CHCR_0 and CHCR_1 as shown in table 13.5. The source of the
transfer request does not have to be the data transfer source or destination.
Содержание HD6417641
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Страница 11: ...Rev 4 00 Sep 14 2005 Page xi of l USB Universal serial bus WDT Watch dog timer...
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Страница 204: ...Section 4 Clock Pulse Generator CPG Rev 4 00 Sep 14 2005 Page 154 of 982 REJ09B0023 0400...
Страница 212: ...Section 5 Watchdog Timer WDT Rev 4 00 Sep 14 2005 Page 162 of 982 REJ09B0023 0400...
Страница 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Страница 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Страница 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Страница 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Страница 500: ...Section 13 Direct Memory Access Controller DMAC Rev 4 00 Sep 14 2005 Page 450 of 982 REJ09B0023 0400...
Страница 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Страница 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Страница 734: ...Section 18 Multi Function Timer Pulse Unit MTU Rev 4 00 Sep 14 2005 Page 684 of 982 REJ09B0023 0400...
Страница 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Страница 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Страница 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Страница 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Страница 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
Страница 1032: ...Rev 4 00 Sep 14 2005 Page 982 of 982 REJ09B0023 0400 X X Y data addressing 52 X Y memory 193...
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