SH7616 Datasheet, PDF (483/935 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7600 Series

Section 10 Ethernet Controller Direct Memory Access Controller (E-DMAC)
10.3.3 Reception
When the receiver is enabled and the CPU sets the receive request bit (RR) in the E-DMAC
receive request register (EDRRR), the E-DMAC reads the descriptor following the previously
used one from the receive descriptor list (in the initial state, the descriptor indicated by the
transmission descriptor start address register (TDLAR)), and then enters the receive-standby state.
If the setting of the RACT bit is “active” and an own-address frame is received, the E-DMAC
transfers the frame to the receive buffer specified by RD2. If the data length of the received frame
is greater than the buffer length given by RD1, the E-DMAC performs write-back to the descriptor
when the buffer is full (RFP = 10 or 00), then reads the next descriptor. The E-DMAC then
continues to transfer data to the receive buffer specified by the new RD2. When frame reception is
completed, or if frame reception is suspended because of an error of some kind, the E-DMAC
performs write-back to the relevant descriptor (RFP = 11 or 01), and then ends the receive
processing. The E-DMAC then reads the next descriptor and enters the receive-standby state
again.
Note: To receive frames continuously, the receive enable control bit (RNC) must be set to 1 in
the receive control register (RCR). After initialization, this bit is cleared to 0.
Rev. 2.00 Mar 09, 2006 page 457 of 906
REJ09B0292-0200