SH7764 Datasheet, PDF (801/1752 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A Series

Section 19 Ethernet Controller (EtherC)
19.4.6 Operation by IPG Setting
The EtherC has a function to change the non-transmission period IPG (Inter Packet Gap) between
transmit frames. By changing the set values of the IPG setting register (IPGR), the transmission
efficiency can be raised and lowered from the standard value. IPG settings are prescribed in
IEEE802.3 standards. When changing settings, adequately check that the respective devices can
operate smoothly on the same network.
Case A
(short IPG)
[1]
[2]
[3]
[4]
[5]
......
Packet IPG*
Case B
(long IPG)
[1]
[2]
[3]
[4]
......
Note: * IPG may be longer than the set value, depending on the state of the line and the system bus.
Figure 19.7 Changing IPG and Transmission Efficiency
19.4.7 Flow Control
The EtherC supports flow control functions conforming to IEEE802.3x for full-duplex operation.
The flow control can be applied to both receive and transmit operations. When transmitting
PAUSE frames, flow control can be performed by the following two procedures :
(1) Automatic PAUSE Frame Transmission
For receive frames, PAUSE frames are automatically transmitted when the number of data written
to the receive FIFO reaches the value set in FCFTR. The TIME parameter included in the PAUSE
frame is set by APR. The automatic PAUSE frame transmission is repeated until the number of
data in the receive FIFO becomes less than the value set in FCFTR as the receive data is read from
the FIFO. Using TPAUSER, the upper limit of retransmission counts of the PAUSE frames can
also be set. In this case, PAUSE frame transmission is repeated until the number of receive FIFO
data becomes less than the FCFTR value, or the number of transmits reaches the value set by
TPAUSER.
The automatic PAUSE frame transmission is enabled when the TXF bit in ECMR is 1.
Rev. 1.00 Nov. 22, 2007 Page 745 of 1692
REJ09B0360-0100