r5s77631ay266bgv Renesas Electronics Corporation., r5s77631ay266bgv Datasheet - Page 1022

Manufacturer Part Number

r5s77631ay266bgv

Renesas 32-bit Risc Microcomputer Superhtm Risc Engine Family Sh-4a Series

Manufacturer

Renesas Electronics Corporation.

Section 23 Gigabit Ethernet Controller (GETHER)

When 11 is written to the TR bits in EDTRR with the TE bit in ECMR set to 1 and there is empty

space of 32 bytes or more in the transmit FIFO, the E-DMAC reads the descriptor following the

previously used descriptor from the transmit descriptor list (or the descriptor indicated by TDLAR

at the initial startup).

If the TACT bit of the read descriptor is set to 1 (valid), the E-DMAC sequentially reads transmit

frame data from the transmit buffer start address specified by TD2 and transfers the data to the

transmit FIFO. The E-DMAC configures a transmit frame and starts transmission to the

GMII/MII/RMII. 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.

• TFP = 10 (start of a frame)

• TFP = 01 or 11 (end of a frame)

• TFP = 00 (frame continued)

As long as the TACT bit of a read descriptor is set to 1 (valid), the reading of E-DMAC

descriptors and the transmission of frames continue.

When a descriptor with the TACT bit cleared to 0 (invalid) is read, the E-DMAC performs the

following processing and completes transmit processing.

• Clears the TR bits in EDTRR to 00.

• Writes the TC bits in EESR to 11 and generates an interrupt to the CPU.

The E-DMAC can store up to four frames of data in the transmit FIFO.

Rev. 1.00 Oct. 01, 2007 Page 956 of 1956

REJ09B0256-0100

Descriptor write-back (writing 0 to the TACT bit) is performed after completion of DMA

Descriptor write-back (writing 0 to the TACT bit and writing status) is performed after

completion of frame transmission.

Descriptor write-back is not performed. The TACT bit retains the value 1.

Transmission Procedure and Processing Flow

Transmission