HD6417618 RENESAS [Renesas Technology Corp], HD6417618 Datasheet - Page 339

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

Maximum
transmit FIFO capacity
Minimum
transmit FIFO capacity
Maximum
transmit FIFO capacity
Minimum
transmit FIFO capacity
However, as stated in step 3, the read access to the transmit FIFO by the EtherC module will
have been terminated, and the E-DMAC thus stops operating with the transmit FIFO full.
In short, this problem arises when [initial value of RP – WP value < length of remaining frame
data] at the point of the transmit underflow.
Figure 12.11 Operation when E-DMAC Stops and the Transmit FIFO
WP
WP
1. Initial state after software reset
3. Transmit-FIFO underflow has occurred
Data for transmission is read by EtherC
Transmit FIFO
Transmit FIFO
Section 12 Ethernet Controller Direct Memory Access Controller (E-DMAC)
RP
RP
Initial state
RP
Increment
2. Writing and reading of the data for transmission
4. Point where the problem makes the E-DMAC stop
WP
WP
Data for transmission is written
by the E-DMAC.
Data for transmission is written
by the E-DMAC.
Reading of data for transmission
by EtherC is terminated.
Data for transmission is read
by EtherC
Rev. 6.00 Jun. 12, 2007 Page 307 of 610
Transmit FIFO
Transmit FIFO
WP: Transmit FIFO write pointer
RP: Transmit FIFO read pointer
Transmit FIFO
is full
Increment
REJ09B0131-0600
RP
RP