DP83952 datasheet(28/90 Pages) NSC

28 / 90 page

50 Functional Description (Continued)

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 RIC II system treats this state in a similar manner

to a receive collision with

PORT M fulfilling the role of the

receiving port The difference from a true receive collision 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 com-

mon with the operation of the

RECEIVE COLLISION state

the repeater remains in this condition until the collision 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 RIC II

which contained

PORT N at the start of packet repetition contains

PORT M during the TRANSMIT COLLISION and ONE PORT LEFT

states

JABBER PROTECTION

A repeater is required to disable transmit activity if the

length of its current transmission reaches the jabber protect

limit This is defined by the specification’s

Tw3 time The

repeater disables output for a time period defined by the

Tw4 specification after this period normal operation may

resume

Figure 5-7 shows the effect of a jabber length packet upon a

RIC II based repeater system The JABBER PROTECT

state is entered from the

SEND DATA state While the Tw4

period is observed the Inter-RIC bus displays the IDLE

state This is misleading since new packet activity or contin-

uous activity (as shown in the diagram) does not result in

packet repetition This may only occur when the

Tw4 re-

quirement has been satisfied

TLF12499 – 13

Note The Inter-RIC bus is configured to use active low signals

FIGURE 5-6 Transmit Collision

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