DP83953VUL National Semiconductor, DP83953VUL Datasheet - Page 23

• Manufacturer Part Number: DP83953VUL
• Description: IC CTRLR RIC REPEATER 160-PQFP
• Manufacturer: National Semiconductor

Specifications of DP83953VUL

• Controller Type: Ethernet Repeater Interface Controller
• Interface: IEEE 802.3
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 870mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-MQFP, 160-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *DP83953VUL

4.0 Functional Description
Receive Collisions (AUI Port only)
A receive collision is a collision which occurs on the net-
work segment attached to the AUI port. The collision is
"received" in a similar manner as a data packet is received,
and then repeated to the other network segments. Not sur-
prisingly, the receive collision propagation follows a similar
sequence of operations as data repetition.
An arbitration process is performed to find PORT N and a
preamble/jam pattern is transmitted by the repeater's other
ports. When the AUI port as PORT N detects a collision on
its segment the COLN Inter-RIC bus signal is asserted.
This forces all the RIC2As in the system to transmit a pre-
amble/jam pattern to their segments. This is important
since they may be already transmitting data from their elas-
ticity buffers. The repeater moves to the RECEIVE COLLI-
SION state and begins to transmit the jam pattern. The
repeater remains in this state until both the following condi-
tions have been fulfilled:
1. at least 96 bits have been transmitted onto the network,
2. the activity has ended.
Under close examination, the repeater specification reveals
that the actual end of activity has its own permutations of
conditions:
1. collision and receive data signals may end simulta-
2. receive data may appear to end before collision signals,
3. receive data may continue for some time after the end of
Network segments using coaxial media may experience
spurious gaps in segment activity when the collision signal
goes inactive. This arises from the inter-action between the
receive and collision signal squelch circuits, implemented
in coaxial transceivers, and the properties of the coaxial
cable itself. The repeater specification avoids propagation
of these activity gaps by extending collision activity by the
Tw2 wait time. Jam pattern transmission must be sustained
throughout this period. After this, the repeater will move to
the WAIT state unless there is a data signal being received
by the AUI port as PORT N.
The functional timing diagram, Figure 7, shows the opera-
tion of a repeater system during a receive collision. The
system configuration is the same as earlier described and
is shown in Figure 6.
The RIC2As perform the same PORT N arbitration and
data repetition operations described previously. The sys-
tem is notified of the receive collision on the AUI port by the
COLN bus signal going active. This signal informs the main
state machines to send out the jam pattern rather than
valid data stored in the elasticity buffers. Once a collision
has occurred, the IRC, IRD and IRE bus signals may
become undefined. When the collision has ended and the
Tw2 operation performed, the repeater moves to the WAIT
state.
Transmit Collisions
A transmit collision is a collision that is detected upon a
segment to which the repeater system is transmitting. The
neously,
the collision signal.
(Continued)
23
port state machine monitoring the colliding segment
asserts the ANYXN bus signal. The assertion of ANYXN
causes PORT M arbitration to begin. The repeater moves
to the TRANSMIT COLLISION state when the port which
had been PORT N starts to transmit a Manchester
encoded 1 on to its network segment. While in the TRANS-
MIT COLLISION state, all ports of the repeater must trans-
mit the 1010... jam pattern, and PORT M arbitration is
performed. Each RIC2A is obligated, by the IEEE specifica-
tion, to ensure all of its ports transmit for at least 96 bits
once the TRANSMIT COLLISION state has been entered.
This transmit activity is enforced by the ANYXN bus signal.
While ANYXN is active, all RIC2A ports will transmit jam.
To ensure this situation lasts for at least 96 bits, the MSM
inside the RIC2As assert the ANYXN signal throughout this
period. After this period has elapsed, ANYXN will only be
asserted if there are multiple ports with active collisions on
their network segments.
There are two possible ways for a repeater to leave the
TRANSMIT COLLISION state. The most straight forward is
when network activity, i.e., collisions and their Tw2 exten-
sions, end before the 96 bit enforced period expires. Under
these conditions the repeater system may move directly to
the WAIT state when 96 bits have been transmitted to all
ports. If the MSM enforced period ends and there is still
one port experiencing a collision, the ONE PORT LEFT
state is entered. This may be seen on the Inter-RIC bus
when ANYXN is de-asserted and PORT M stops transmit-
ting to its network segment. In this circumstance the Inter-
RIC bus transitions to the RECEIVE COLLISION state.
The repeater will remain in this state while PORT M's colli-
sion, Tw2 collision extension and any receive signals are
present. When these conditions are not true, packet repeti-
tion finishes and the repeater enters the WAIT state.
Figure 8 shows a multi-RIC2A system operating under
transmit collision conditions. There are many different sce-
narios which may occur during a transmit collision, this fig-
ure illustrates one of these. The diagram begins with
packet reception by port A1. Port B1 experiences a colli-
sion, since it is not PORT N it asserts ANYXN. This alerts
the main state machines in the system to switch from data
to jam pattern transmission.
Port A1 is also monitoring the ANYXN bus line. Its asser-
tion forces A1 to relinquish its PORT N status, start trans-
mitting, stop asserting ACTN and release its hold on the
PSM arbitration signals (ACKO A and ACKI B). The first bit
it transmits will be a Manchester encoded "1" in the jam
pattern. Since port B1 is the only port with a collision, it
attains PORT M status and stops asserting ANYXN. It
does however assert ACTN, and exert its presence upon
the PSM arbitration chain (forces ACKO B low). The MSMs
ensure that ANYXN stays active and thus force all of the
ports, including PORT M, to transmit to their segments.
After some time port A1 experiences a collision. This arises
from the presence of the packet being received from port
A1's segment and the jam signal the repeater is now trans-
mitting onto this segment. Simultaneous receive and trans-
mit activity on one segment results in a collision. Port A1
fulfills the same criteria as B1, i.e., it has an active collision
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