CS89712-CB View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
CS89712-CB Datasheet PDF : 170 Pages
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CS89712
If the CS89712 commits buffer space to a particular
transmit frame, it will not allow subsequent frames
to be written to that buffer space as long as the
transmit frame is committed.
After buffer space is committed, the frame is sub-
sequently transmitted unless any of the following
occur:
1) The software completely writes the frame data,
but transmission failed on the Ethernet line.
There are three such failures, and these are in-
dicated by three bits in the TxEvent register:
16coll, Jabber, or Out-of-Window.
or:
2) The software aborts the transmission by setting
the Force (TxCMD register bit 8) bit. In this
case, the committed transmit frame, as well as
any yet-to-be-transmitted frames queued in the
on-chip memory, are cleared and not transmit-
ted. The software should make TxLength = 0
when using the Force bit.
or:
3) There is a transmit under-run while the Tx-
Underrun bit (BufEvent register bit 9) is set.
Successful transmission is indicated when the
TxOK bit (TxEvent register bit 8) is set.
2.34.11 Transmit Frame Length
The length of the frame transmitted is determined
by the value written into the TxLength register
during the Transmit Request. The length of the
transmit frame may be modified by the configura-
tion of the TxPadDis bit (TxCMD register bit D)
and the InhibitCRC bit (TxCMD register bit C).
Table 30 defines how these bits affect the length of
the transmit frame, and details which frames will
be sent.
2.35 Full Duplex Considerations
The driver should not bid to transmit a long frame
(i.e., a frame greater than 118 bytes) if the prior
transmit frame is still being transmitted. The end of
the transmission of this prior frame is indicated by
a TxOK bit being set in the TxEvent register.
TxCMD register
TxPadDis InhibitCRC
(Bit D)
(Bit C)
0
0
0
1
1
0
1
1
Software specified transmit length at 0146h (in bytes)
3 < TxLength
< 60
60 < TxLength
< 1514
1514 < TxLength
< 1518
TxLength
> 1518
Pad to 60 and add Send frame and add
CRC
CRC [Normal Mode]
Will not send
Will not send
Pad to 60 and send Send frame without
without CRC
CRC
Send frame
without CRC
Will not send
Send without pads, Send frame and add
and add CRC
CRC
Will not send
Will not send
Send without pads
and without CRC
Send frame without
CRC
Send frame
without CRC
Will not send
Notes: 1. If the TxPadDis bit is clear and InhibitCRC is set and the CS89712 is commanded to send a frame of
length less than 60 bytes, the CS89712 pads.
2. The CS89712 will not send a frame with TxLength less than 3 bytes.
Table 30. Transmit Frame Length
66
DS502PP2
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