CRD8900A-1 Cirrus Logic Inc, CRD8900A-1 Datasheet - Page 34

• 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

3.9.5.4 Collision Resolution
If a collision is detected while the CS8900A is
transmitting, the MAC responds in one of three
ways depending on whether it is a normal col-
lision (within the first 512 bits of transmission)
or a late collision (after the first 512 bits of
transmission):
3.9.5.5 Normal Collisions
If a collision is detected before the end of the
preamble and SFD, the MAC finishes the pre-
amble and SFD, transmits the jam sequence
(32-bit pattern of all 0’s), and then initiates
Backoff. If a collision is detected after the
transmission of the preamble and SFD but be-
34
Ready and Not
in Backoff?
Yes
Fra m e
Tx
Figure 11. Simple Deferral
Yes
Start Monitoring
Network Activity
No
No
Network
Active?
9.6 μ s
Wait
Transmit
No
Frame
Network
Active?
CIRRUS LOGIC PRODUCT DATASHEET
Yes
fore 512 bit times, the MAC immediately termi-
nates
sequence, and then initiates Backoff. In either
case, if the Onecoll bit (Register 9, TxCMD, Bit
9) is clear, the MAC will attempt to transmit a
packet a total of 16 times (the initial attempt
plus 15 retransmissions) due to normal colli-
sions. On the 16th collision, it sets the 16coll
bit (Register 8, TxEvent, Bit F) and discards
the packet. If the Onecoll bit is set, the MAC
discards the packet without attempting any re-
transmission.
3.9.5.6 Late Collisions
If a collision is detected after the first 512 bits
have been transmitted, the MAC immediately
terminates transmission, transmits the jam se-
quence, discards the packet, and sets the Out-
of-window bit (Register 8, TxEvent, Bit 9). The
CS8900A does not initiate backoff or attempt
to retransmit the frame. For additional informa-
tion about Late Collisions, see Out-of-Window
Error in this section.
3.9.5.7 Backoff
After the MAC has completed transmitting the
jam sequence, it must wait, or “Back off”, be-
fore attempting to transmit again. The amount
of time it must wait is determined by one of two
Backoff algorithms: the Standard Backoff algo-
rithm (ISO/IEC 4.2.3.2.5) or the Modified
Backoff algorithm. The host selects which al-
gorithm through the ModBackoffE bit (Register
13, LineCTL, Bit B).
3.9.5.8 Standard Backoff
The Standard Backoff algorithm, also called
the “Truncated Binary Exponential Backoff”, is
described by the equation:
where r (a random integer) is the number of
slot times the MAC must wait (1 slot time = 512
transmission,
Crystal LAN™ Ethernet Controller
0 ≤ r ≤ 2
transmits
k
CS8900A
the
DS271F5
jam