HD6417618 RENESAS [Renesas Technology Corp], HD6417618 Datasheet - Page 323

• Manufacturer Part Number: HD6417618
• Description: 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7618 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

(b) Receive Descriptor 1 (RD1)
RD1 specifies the receive buffer length (maximum 64 kbytes).
(c)
RD2 specifies the 32-bit receive buffer start address. The receive buffer start address must be
aligned with a longword boundary. However, when SDRAM is connected, it must be aligned with
a 16-byte boundary.
12.3.2
When the transmit function is enabled and the transmit request bit (TR) is set in the E-DMAC
transmit request register (EDTRR), the E-DMAC reads the descriptor used last time from the
transmit descriptor list (in the initial state, the descriptor indicated by the transmission descriptor
start address register (TDLAR)). If the setting of the TACT bit in the read descriptor is active, the
E-DMAC reads transmit frame data sequentially from the transmit buffer start address specified
by TD2, and transfers it to the EtherC. The EtherC creates a transmit frame and starts transmission
to the MII. After DMA transfer of data equivalent to the buffer length specified in the descriptor,
the following processing is carried out according to the TFP value.
Bit
31 to 16
15 to 0
Receive Descriptor 2 (RD2)
Transmission
Bit Name
RBL
RDL
Initial
value
All 0
All 0
Section 12 Ethernet Controller Direct Memory Access Controller (E-DMAC)
R/W
R/W
R/W
Receive Buffer Length
These bits specify the maximum reception byte length
in the corresponding receive buffer.
The transfer byte length must align with a 16-byte
boundary (bits 19 to 16 cleared to 0). The maximum
receive frame length with one frame per buffer is
1,514 bytes, excluding the CRC data. Therefore, for
the receive buffer length specification, a value of
1,520 bytes (H'05F0) that takes account of a 16-byte
boundary is set as the maximum receive frame
length.
Receive Data Length
These bits specify the data length of a receive frame
stored in the receive buffer.
The receive data transferred to the receive buffer
does not include the 4-byte CRC data at the end of
the frame. The receive frame length is reported as the
number of words (valid data bytes) not including this
CRC data.
Description
Rev. 6.00 Jun. 12, 2007 Page 291 of 610
REJ09B0131-0600