Renesas H8S Family, Hardware Manual

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Section 21 Ethernet Controller Direct Memory Access Controller (E-DMAC)
Rev. 1.00 Mar. 12, 2008 Page 822 of 1178
REJ09B0403-0100
(a) Receive Descriptor 0 (RD0)
RD0 indicates the receive frame status. The CPU and E-DMAC use RD0 to report the frame
receive status.
Bit Bit Name
Initial
value
R/W Description
31 RACT 0 R/W Receive Descriptor Active
Indicates that this descriptor is active. The E-DMAC
resets this bit after receive data has been transferred
to the receive buffer. On completion of receive frame
processing, the CPU sets this bit to prepare for
reception.
0: The receive descriptor is invalid.
Indicates that the receive buffer is not ready
(access disabled by E-DMAC), or this bit has been
reset by a write-back operation on termination of
E-DMAC frame transfer processing (completion or
suspension of reception).
If this state is recognized in an E-DMAC descriptor
read, the E-DMAC terminates receive processing
and receive operations cannot be continued.
Reception can be restarted by setting RACT to 1
and executing receive initiation.
1: The receive descriptor is valid
Indicates that the receive buffer is ready (access
enabled) and processing for frame transfer from
the FIFO has not been executed, or that frame
transfer is in progress.
When this state is recognized in an E-DMAC
descriptor read, the E-DMAC continues with the
receive operation.
30 RDLE 0 R/W Receive Descriptor List Last
After completion of the corresponding buffer transfer,
the E-DMAC references the first receive descriptor.
This specification is used to set a ring configuration
for the receive descriptors.
0: This is not the last receive descriptor list
1: This is the last receive descriptor list