Section 10 Ethernet Controller Direct Memory Access Controller (E-DMAC)
Rev. 2.00 Mar 09, 2006 page 448 of 906
REJ09B0292-0200
10.3
Operation
The E-DMAC is connected to the EtherC, and performs efficient transfer of transmit/receive data
between the EtherC and memory (buffers) without the intervention of the CPU. The E-DMAC
itself reads control information, including buffer pointers called descriptors, relating to the buffers.
The E-DMAC reads transmit data from the transmit buffer and writes receive data to the receive
buffer in accordance with this control information. By setting up a number of consecutive
descriptors (a descriptor list), it is possible to execute transmission and reception continuously.
10.3.1
Descriptor List and Data Buffers
Before starting transmission/reception, the communication program creates transmit and receive
descriptor lists in memory. The start addresses of these lists are then set in the transmit and receive
descriptor list start address registers.
Transmit Descriptor
Figure 10.2 shows the relationship between a transmit descriptor and the transmit buffer.
According to the specification in this descriptor, the relationship between the transmit frame and
transmit buffer can be defined as one frame/one buffer or one frame/multi-buffer.
Notes: 1. The descriptor’s start address setting must be aligned with an address boundary that
corresponds with the descriptor’s length as set by the E-DMAC mode register
(EDMR).
2. The transmit buffer’s start address setting must be aligned with a longword boundary.
However, when SDRAM is connected, the setting must be aligned with a 16-byte
boundary.
Transmit descriptor
Transmit buffer
TACT
TDLE
TFP1
TFP0
TFE
TFS26 to TFS0
0
0
31
16
31
31 30 29 28 27 26
TD0
TDL
TD1
TBA
Padding (4 bytes)
TD2
Valid transmit data
Figure 10.2 Relationship between Transmit Descriptor and Transmit Buffer
Содержание SH7616
Страница 10: ...Rev 2 00 Mar 09 2006 page x of xxvi ...
Страница 132: ...Section 2 CPU Rev 2 00 Mar 09 2006 page 106 of 906 REJ09B0292 0200 ...
Страница 568: ...Section 12 16 Bit Free Running Timer FRT Rev 2 00 Mar 09 2006 page 542 of 906 REJ09B0292 0200 ...
Страница 582: ...Section 13 Watchdog Timer WDT Rev 2 00 Mar 09 2006 page 556 of 906 REJ09B0292 0200 ...
Страница 662: ...Section 14 Serial Communication Interface with FIFO SCIF Rev 2 00 Mar 09 2006 page 636 of 906 REJ09B0292 0200 ...
Страница 706: ...Section 16 Serial I O SIO Rev 2 00 Mar 09 2006 page 680 of 906 REJ09B0292 0200 ...
Страница 820: ...Section 19 Pin Function Controller PFC Rev 2 00 Mar 09 2006 page 794 of 906 REJ09B0292 0200 ...
Страница 932: ...Appendix D Package Dimensions Rev 2 00 Mar 09 2006 page 906 of 906 REJ09B0292 0200 ...
Страница 935: ...SH7616 Hardware Manual ...