DP83955AV National Semiconductor, DP83955AV Datasheet - Page 26

• Manufacturer Part Number: DP83955AV
• Description: IC CTRLR RIC REPEATER 100-PQFP
• Manufacturer: National Semiconductor
• Series: LERIC™r

Specifications of DP83955AV

• Controller Type: LitE Repeater Interface Controller
• Voltage - Supply: 5V
• Current - Supply: 250mA
• Mounting Type: Surface Mount
• Package / Case: 84-LCC (J-Lead)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Operating Temperature: -
• Interface: -
• Other names: *DP83955AV

PORT M arbitration to begin The repeater moves to the
TRANSMIT COLLISION state when the port which had
SION state all ports of the repeater must transmit the
MIT COLLISION state has been entered This transmit ac-
TRANSMIT COLLISION state The most straightforward is
Figure 5-6 shows a multi-LERIC system operating under
5 0 Functional Description
Transmit Collisions
A transmit collision is a collision that is detected upon a
segment to which the repeater system is transmitting The
port state machine monitoring the colliding segment asserts
the ANYXN bus signal The assertion of ANYXN causes
been PORT N starts to transmit a Manchester encoded 1
on to its network segment While in the TRANSMIT COLLI-
1010
Each LERIC is obliged by the IEEE specification to ensure
all of its ports transmit for at least 96 bits once the TRANS-
tivity is enforced by the ANYXN bus signal While ANYXN is
active all LERIC ports will transmit jam To ensure this situa-
tion lasts for at least 96 bits the MSMs inside the LERICs
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 seg-
ments
There are two posible ways for a repeater to leave the
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-LERIC bus when
ANYXN is deasserted and PORT M stops transmitting to its
network segment In this circumstance the Inter-LERIC bus
transitions to the RECEIVE COLLISION state The repeater
will remain in this state while PORT M’s collision Tw2 colli-
sion extension and any receive signals are present When
these conditions are not true packet repetition finishes and
the repeater enters the WAIT state
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
jam pattern and PORT M arbitration is performed
(Continued)
26
PORT M status and stops asserting ANYXN It does howev-
reception by port A1 Port B1 experiences a collision 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 assertion
forces A1 to relinquish its PORT N status start transmitting
stop asserting ACTN and release its hold on the PSM arbi-
tration signals (ACKO A and ACKI B) The first bit it trans-
mits will be a Manchester encoded ‘‘1’’ in the jam pattern
Since port B1 is the only port with a collision it attains
er assert ACTN and exert its presence upon the PSM arbi-
tration chain (forces ACKO B low) The MSMs ensure that
ANYXN stays active and thus forces all of the ports includ-
ing 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 plus the jam signal the repeater is now trans-
mitting onto this segment Two packets on one segment
results in a collision PORT M now moves from B1 to A1
Port A1 fulfills the same criteria as B1 (i e it has an active
collision on its segment) but in addition it is higher in the
arbitration chain This priority yields no benefits for port A1
since the ANYXN signal is still active There are now two
sources driving ANYXN the MSMs and the collision on port
B1
Eventually the collision on port B1 ends and the ANYXN
extension by the MSMs expires There is only one collision
on the network (this may be deduced since ANYXN is inac-
tive) so the repeater will move to the ONE PORT LEFT
state The LERIC system treats this state in a similar man-
ner to a receive collision with PORT M fulfilling the role of
the receiving port The difference from a true receive colli-
sion is that the switch from packet data to the jam pattern
has already been made (controlled by ANYXN) Thus the
state of COLN has no effect upon repeater operations In
common with the operation of the RECEIVE COLLISION
state the repeater remains in this condition until the colli-
sion and receive activity on PORT M subside The packet
repetition operation completes when the Tw1 recovery time
in the WAIT state has been performed
Note In transmit collision conditions COLN will only go active if the LERIC
PORT M during the TRANSMIT COLLISION and ONE PORT LEFT
which contained PORT N at the start of packet repetition contains
states