SH7616 Datasheet, PDF(477/935 Page) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7600 Series

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SH7616 Datasheet, PDF (477/935 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7600 Series

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Section 10 Ethernet Controller Direct Memory Access Controller (E-DMAC)

Transmit Descriptor 1 (TD1): Specifies the transmit buffer length (maximum 64 kbytes).

Bits 31 to 16âTransmit Buffer Data Length (TDL): These bits specify the valid transfer byte

length in the corresponding transmit buffer.

Note: When the one frame/multi-buffer system is specified (TD0 and TFP = 10 or 00), the

transfer byte length specified in the descriptors at the start and midway can be set in byte

units.

Bits 15 to 0âReserved: The bits are always read as 0. The write value should always be 0.

Transmit Descriptor 2 (TD2): Specifies the 32-bit transmit buffer start address.

Note: The transmit bufferâs 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.

Bits 31 to 0âTransmit Buffer Address (TBA)

Receive Descriptor

Figure 10.3 shows the relationship between a receive descriptor and the receive buffer. In frame

reception, the E-DMAC performs data rewriting up to a receive buffer 16-byte boundary,

regardless of the receive frame length. Finally, the actual receive frame length is reported in the

lower 16 bits of RD1 in the descriptor. Data transfer to the receive buffer is performed

automatically by the E-DMAC to give a one frame/one buffer or one frame/multi-buffer

configuration according to the size of one received frame.

Notes: 1. The descriptorâs start address setting must be aligned with an address boundary that

corresponds with the descriptorâs length as set by the E-DMAC mode register

(EDMR).

2. The receive bufferâs 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. Make the setting so that the size of the receive buffer is aligned with a 16-

byte boundary.

Example:

H'0500 (= 1280 bytes)

Rev. 2.00 Mar 09, 2006 page 451 of 906

REJ09B0292-0200

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