LAN83C175 Datasheet, PDF (55/92 Pages) SMSC Corporation – Ethernet CARDBUS Integrated Controller With Modem Support

D0 - CardBus TRANSMIT DMA DATA
LENGTH / CONTROL BITS
Reset Value: xxxxxxxxxxxxxxxxxxxx
This register contains the number of bytes
remaining in the current data buffer being read
by the transmit DMA. This register is a down
counter and is decremented by the number of
bytes copied each time data is read from the
buffer. The transmit DMA control bits may
also be read and written through this I/O port.
31 through 22 - Unused.
21 - OWNER: Indicates whether the last
descriptor read was owned by the NIC (1) or
the host (0). This bit is read only at this
location. It may be written through the
PTSTAT register.
20 - LASTDESCR: Indicates that this is the
last descriptor for the current transmit frame
(Not used when FRAGLIST = 1).
19 - NOCRC: Disable automatic CRC
generation for this packet when set.
18 - IAF: When set, interrupt after this frame
is transmitted.
17 - LFFORM: Fragment list format - a 1
indicates that the data length field comes
before the pointer in the fragment list. A 0
indicates that the pointer comes before the
data length.
16 - FRAGLIST: Indicates that this descriptor
points to a fragment list.
15 through 0 - Buffer Length.
D4 - CardBus TRANSMIT FRAGMENT COUNT
Reset Value: XXXXXX
This register contains the number of fragments in
the current transmit DMA fragment list. It is
decremented just before each fragment is read.
31 through 6 - Unused.
5 through 0 - Fragment Count.
D8 -- CardBus TRANSMIT RAM CURRENT
ADDRESS
Reset Value: 00000000000
This register contains the byte address of the data
currently being accessed in the local transmit
RAM.
31 through 18 - Unused.
10 through 0 - RX RAM Address.
DC - EARLY TRANSMIT THRESHOLD
Reset Value: XXXXXXXXXXX
This register is programmed with the early
transmit threshold for the LAN83C175.
Transmission on the network will begin after the
number of bytes specified in this register have
been loaded into the local transmit RAM. Bits 1
and 0 are ignored, so the granularity of the
threshold is four bytes. Data written into this
register will automatically be stored in the early
transmit count register at the same time. The
register should only be written at initialization
time.
31 through 11: Unused.
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