SH7763 Datasheet, PDF (1037/2026 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A Series

Section 23 Gigabit Ethernet Controller (GETHER)
23.4.6 Transmit/Receive Processing of Multi-Buffer Frame (Single-Frame/Multi-
Descriptor)
(1) Multi-Buffer Frame Transmit Processing
If an error occurs during multi-buffer frame transmission, the processing shown in figure 23.12 is
carried out by the E-DMAC.
In the figure where the transmit descriptor is shown as inactive (TACT bit = 0), buffer data has
already been transmitted successfully, and where the transmit descriptor is shown as active (TACT
bit = 1), buffer data has not been transmitted. If a frame transmit error occurs in the first descriptor
part where the transmit descriptor is active (TACT bit = 1), transmission is halted, and the TACT
bit is cleared to 0, immediately. The next descriptor is then read, and the position within the
transmit frame is determined on the basis of bits TFP1 and TFP0 (continuing [B′00] or end
[B′01]). In the case of a continuing descriptor, the TACT bit is cleared to 0, and the next
descriptor is read immediately. If the descriptor is the final descriptor, not only is the TACT bit
cleared to 0, but write-back is also performed to the TFE and TFS bits at the same time. Data in
the buffer is not transmitted between the occurrence of an error and write-back to the final
descriptor. If error interrupts are enabled in EESIPR, an interrupt is generated immediately after
the final descriptor write-back.
Descriptors
TT TT
A D F F ^Frame
C L P P Type
TE 10
E-DMAC
Inacrivates TACT (change 1 to 0)
Descriptor read
Inactivates TACT
Descriptor read
Inactivates TACT
Descriptor read
Inactivates TACT
Descriptor read
Inactivates TACT
0 0 1 0 Start
0 0 0 0 Continune
0 0 0 0 Continune
1 0 0 0 Continune
1 0 0 0 Continune
1 0 0 0 Continune
1 0 0 0 Continune
10 01
11 10
End
Start
Transmit error
occurrence
Utransmitted
data is not
transmitted
after error
occurrence.
Descriptor is
only processed
One frame
Buffer length set
by descriptor
Transmitted data
Untransmitted dara
Figure 23.12 E-DMAC Operation after Transmit Error
Rev. 1.00 Oct. 01, 2007 Page 971 of 1956
REJ09B0256-0100