SH7713 datasheet(747/904 Pages) RENESAS

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Section 19 Ethernet Controller Direct Memory Access Controller (E-DMAC)

Rev.1.50 Aug. 30, 2006 Page 707 of 860

REJ09B0288-0150

(b)

Receive Descriptor 1 (RD1)

In RD1, the user specifies the data length of a receive buffer usable by the corresponding

descriptor. After reception of a frame, RD1 indicates the length of a frame received by the

E-DMAC.

The user should set RD1 before the start of a read by the E-DMAC.

Bit

Bit Name

Initial

Value

R/W

Description

31 to 16

RBL

All 0

R/W

Receive Buffer Data Length (in bytes, to be specified

on 16-byte boundary)

Set the length of data that can be received by the

corresponding receive buffer in bytes.

Set a receive buffer length on a 16-byte boundary

(with bits 19 to 16 cleared to 0).

In single-frame/single-buffer (descriptor) operation,

the maximum receive frame length excluding CRC

data is 1514 bytes. When specifying a receive buffer

length, set 1520 bytes (H'05F0), which is determined

considering the maximum receive frame length and a

16-byte boundary.

15 to 0

RDL

All 0

Receive Data Length

Indicate the data length of a receive frame stored in

the receive buffer.

Receive data transferred to the receive buffer does

not include CRC data (4 bytes) placed at the end of a

frame. As a receive frame length, the number of bytes

(valid data bytes) not including CRC data are

reported.

In single-frame/multi-buffer (descriptor) operation,

only the receive data length of the last descriptor is

valid. The receive data length of an intermediate

descriptor has no meaning.

(c)

Receive Descriptor 2 (RD2)

RD2 indicates the start address of the corresponding 32-bit width receive buffer. Set the start

address of a receive buffer on a longword boundary. When an SDRAM is connected, set the start

address of a receive buffer on a 16-byte boundary.

The user should set RD2 before the start of a read by the E-DMAC.

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