HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 462

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

Rx Descriptor 1 (RD1): Specifies the receive buffer length (maximum 64 kbytes).
Bits 31 to 16—Receive Buffer Length (RBL): These bits specify the maximum transfer byte
length in the corresponding receive buffer.
Notes: The transfer byte length must align with a 16-byte boundary (bits 19 to 16 cleared to 0).
Bits 15 to 0—Rx Data Length (RDL): These bits specify the data length of a receive frame stored
in the receive buffer.
Note: The receive data transferred to the receive buffer does not include the 4-byte CRC data at
Rx Descriptor 2 (RD2): Specifies the 32-bit receive buffer start address.
Note: The address specification must align with a 16-byte boundary.
Bits 31 to 0—Rx Buffer Address (RBA)
10.3.2
When the transmitter 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.
1. TFP = 00 or 01 (frame continuation):
2. TFP = 01 or 11 (frame end):
Descriptor write-back is performed after DMA transfer.
Descriptor write-back is performed after completion of frame transmission.
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.
the end of the frame. The receive frame length is reported as the number of words (valid
data bytes) not including this CRC data.
Transmission
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