HD6417618 RENESAS [Renesas Technology Corp], HD6417618 Datasheet - Page 327

• Manufacturer Part Number: HD6417618
• Description: 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7618 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

12.3.4
Multi-Buffer Frame Transmit Processing
If an error occurs during multi-buffer frame transmission, the processing shown in figure 12.6 is
carried out by the E-DMAC.
Where the transmit descriptor is shown as inactive (TACT bit = 0) in the figure, buffer data has
already been transmitted normally, 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 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, only, 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 the EtherC/E-DMAC status interrupt permission register (EESIPR), an
interrupt is generated immediately after the final descriptor write-back.
E-DMAC
Inactivates TACT and writes TFE, TFS
Inactivates TACT (change 1 to 0)
Multi-Buffer Frame Transmit/Receive Processing
Descriptor read
Descriptor read
Descriptor read
Descriptor read
Figure 12.6 E-DMAC Operation after Transmit Error
Inactivates TACT
Inactivates TACT
Inactivates TACT
Section 12 Ethernet Controller Direct Memory Access Controller (E-DMAC)
T
A
C
T
0
0
0
1
1
1
1
1
1
D
T
L
E
0
0
0
0
0
0
0
0
1
Descriptors
P
T
F
1
1
0
0
0
0
0
0
0
1
T
F
P
0
0
0
0
0
0
0
0
1
0
Rev. 6.00 Jun. 12, 2007 Page 295 of 610
Untransmitted
data is not
transmitted
after error
occurrence
Descriptor is
only processed.
One frame
REJ09B0131-0600
Buffer
Transmit error
occurrence
Transmitted data
Untransmitted data