SH7763 Datasheet, PDF (1035/2026 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A Series

Section 23 Gigabit Ethernet Controller (GETHER)
23.4.5 CAM Function
Frames input to the E-MAC are grouped into the following four types; unicast for this LSI,
broadcast, multicast, and unicast to other destinations. The MAC addresses of unicast for this LSI
and broadcast are fixed, and determined only by register settings. Consequently, only multicast
and unicast to other destinations determine whether to receive or not and whether to transfer or not
by using the CAM (unicast frames whose destination MAC addresses match this LSI are called
unicast frames to this LSI, and those that do not are called unicast frames to other destinations).
Furthermore, the evaluation of receive and relay of unicast to other destinations and multicast
frames by using CAM are performed by referencing the registered MAC addresses of the CAM
entry table in the TSU. By using this function, receive FIFO overflow can be prevented caused by
accumulation of frame data not required for reception, and CPU processing for determining
receive can be reduced.
The POST table is composed of 4 bits, and each bit corresponds to port 0 reception, port 1
reception, port 0 to port 1 relay, and port 1 to port 0 relay. When the corresponding bit is set to 1,
the CAM evaluation results are used for determining receive and relay. In other words, when the
corresponding bit of the POST table is cleared to 0, receive and relay evaluation will be the same
as when CAM is not used shown in table 23.4.
The on-chip CAM has entry tables which can register the MAC address of 32 entries, the details
of which can be set by TSU_ADRH0 to TSU_ADRH31 and TSU_ADRL0 to TSU_ADRL31. The
setting to enable/disable referencing of the on-chip CAM entry table is performed by the CAM
entry table enable setting register which sets whether to perform CAM evaluation or not, and the
CAM entry table POST setting register for setting whether to use the CAM determination results
for determining receive or relay. When on-chip CAM entry table referencing during receive is
enabled, the destination address in the frame and MAC address registered in the CAM entry table
are compared, and it is determined whether to transfer the frames input to the E-MAC to E-DMAC
(have E-DMAC receive the frames) or discard the frames. When relaying and CAM entry table
referencing during relay are both enabled, whether to transfer or discard multicast frames and
frames for destinations other than this LSI can be determined by comparing the destination
address in the frame and MAC address registered in the CAM entry table. Table 23.5 shows the
processing method of frames (receive or discard) in reception from E-MAC0 to E-DMAC0 or that
from E-MAC1 to E-DMAC1, while table 23.6 shows the processing for frames in relay from E-
MAC0 to E-MAC1 or that from E-MAC1 to E-MAC0 (relay or discard).
Rev. 1.00 Oct. 01, 2007 Page 969 of 1956
REJ09B0256-0100