LAN83C175 Datasheet, PDF (17/92 Pages) SMSC Corporation – Ethernet CARDBUS Integrated Controller With Modem Support

Maximum Transmit Size and Burst Rate
The transmit DMA supports frame sizes up to
64 Kbytes. The maximum size for a single
data buffer (fragment) is also 64 Kbytes. The
transmit DMA will run at the maximum
CardBus data rate of 132 MBytes/s when the
target memory system supports zero wait
state reads. The transmit DMA will burst as
many words as it can before having to
relinquish the CardBus bus. It is capable of
bursting data continuously with no wait states
(even when a transmission is active on the
network) until the transmit RAM becomes full.
The transmit DMA, however, will most likely
lose possession of the CardBus bus several
times before it can fill the entire 1.5 Kbyte
transmit buffer.
Bit Number and Description
31 Through 4 - Unused
5 through 0 - Number of fragments in this
fragment list (1-63). (Note: programming 0
into this field results in 64 fragments).
Data Buffer Pointer
31 through 0 - Starting address of data buffer in
host memory space. Data buffer may be aligned
on any byte.
31 through 16 - Unused
15 through 0 - Length of data buffer.
RECEIVE DMA
The diagram below shows the format of the
receive descriptor table:
31
0
RX LENGTH
RX STATUS
BUFFER ADDRESS
CONTROL
BUF LENGTH
NEXT DESCRIPTOR ADDRESS
17