CRD8900A-1 Cirrus Logic Inc, CRD8900A-1 Datasheet - Page 105

• Manufacturer Part Number: CRD8900A-1
• Description: KIT EVAL FOR CS8900A
• Manufacturer: Cirrus Logic Inc
• Series: CrystalLAN™r

Specifications of CRD8900A-1

• Main Purpose: Interface, Ethernet
• Utilized Ic / Part: CS8900A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Other names: 598-1163

DS271F5
not set). Also, the Rdy4Tx bit is used with in-
terrupts and requires the Rdy4TxiE bit be set.
Figure 30 provides a diagram of error free
transmission without collision.
5.6.10 Committing Buffer Space to a
Transmit Frame
When the host issues a transmit request, the
CS8900A checks the length of the transmit
frame to see if there is sufficient on-chip buffer
space. If there is, the CS8900A sets the
Rdy4TxNOW bit. If not, and the Rdy4TxiE bit
is set, the CS8900A waits for buffer space to
free up and then sets the Rdy4Tx bit. If
Rdy4TxiE is not set, the CS8900A sets the
Rdy4TxNOW bit when space becomes avail-
able.
Even though transmit buffer space may be
available, the CS8900A does not commit buf-
fer space to a transmit frame until all of the fol-
lowing are true:
1) The host must issues a Transmit Request;
2) The Transmit Request must be successful;
3) Either the host reads that the Rdy4TxNOW
If the CS8900A commits buffer space to a par-
ticular transmit frame, it will not allow subse-
quent frames to be written to that buffer space
as long as the transmit frame is committed.
After buffer space is committed, the frame is
subsequently transmitted unless any of the fol-
lowing occur:
1) The host completely writes the frame data,
CS8900A
Crystal LAN™ Ethernet Controller
and,
bit (Register 18, BusST, Bit 8) is set, or the
host reads that the Rdy4Tx bit (Register C,
BufEvent, bit 8) is set.
but transmission failed on the Ethernet line.
There are three such failures, and these
are indicated by three transmit error bits in
CIRRUS LOGIC PRODUCT DATASHEET
Or:
2) The host aborts the transmission by setting
Or:
3) There is a transmit under-run, and the Tx-
Successful transmission is indicated when the
TxOK bit (Register 8, TxEvent, Bit 8) is set.
5.6.11 Transmit Frame Length
The length of the frame transmitted is deter-
mined by the value written into the TxLength
register (PacketPage base + 0146h) during
the Transmit Request. The length of the trans-
mit frame may be modified by the configura-
tion of the TxPadDis bit (Register 9, TxCMD,
Bit D) and the InhibitCRC bit (Register 9, TxC-
MD, Bit C). Table 36 defines how these bits af-
fect the length of the transmit frame. In
addition, it shows which frames the CS8900A
will send.
5.7 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 transmit-
ted. The end of the transmission of this prior
frame is indicated by a TxOK bit being set in
the TxEvent register (register 8).
5.8 Auto-Negotiation Considerations
When the CS8900A is connected to an auto
negotiation hub, and if auto-media detection is
selected (bits 8 and 9 of register 13), then the
the TxEvent register (Register 8): 16coll,
Jabber, or Out-of-Window.
the Force (Register 9, TxCMD, 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 transmitted. The host should make
TxLength = 0 when using the Force bit.
Underrun bit (Register C, BufEvent, Bit 9)
is set.
105