Mitel NWK954 Basic Repeater Function, Jabber Protection, Auto-Partition Function, Expansion Port

Basic Repeater Function

The Repeater Controller monitors activity on the 4 twisted pair ports and on the Expansion Port. When a packet is received on one of the twisted pair ports it is forwarded to the other 3 twisted pair ports and to the Expansion Port. When a packet is received on the Expansion Port it is forwarded to all 4 twisted pair ports. When receive activity is detected on 2 or more ports the Repeater Controller will send the jam signal to all twisted pair ports for the duration of all activity associated with the collision event.

Jabber Protection

The Repeater Controller provides receive jabber protection to ensure that the network is not disrupted by excessively long data streams. If a received data stream exceeds 65,536 bit times then the receiving port will be shutdown. In the shutdown state data received on the faulty port is ignored and packets received from other ports are not transmitted to the faulty port. A port will recover from the shutdown state when the incoming data stream ends or if the device is reset.

Auto-Partition Function

The auto-partition function prevents faulty behaviour on a network segment from disrupting the entire network. The Repeater Controller counts consecutive collisions on each port and will partition a port that causes more than 60 consecutive collisions. In the partitioned state, packets received on the faulty port will be ignored but packets received from other ports will continue to be transmitted to the faulty port. The port will recover from the partitioned state when valid activity is detected on the port or if the device is reset.

Carrier Integrity Monitor

The Repeater Controller detects false carrier events on all ports. A false carrier is defined as receive activity that does not commence with the correct start-of-packet sequence. When a false carrier event is detected, the Repeater Controller will transmit the jam signal on all ports for the duration of the false carrier event provided it does not exceed 450-500 bit times. After this time the port will be isolated and the jam signal will cease. The NWK954 will also isolate a port that suffers 2 successive false carrier events. In the isolated state, packets received from the faulty port are ignored and packets received from other ports are not transmitted to the faulty port. A port will recover from the isolated state when a valid inter-packet gap is detected and is followed by either a valid packet exceeding 450- 500 bit times or by an idle sequence exceeding 33000 (±25%) bit times.

Expansion Port

The Expansion Port allows up to 6 NWK954s to be cascaded. This allows a 24-port hub to be built with no additional external components. The Expansion Port includes a 5-bit parallel bidirectional data bus (IRD) which carries unscrambled symbol data and a 25MHz sampling clock (BPCLK). Each NWK954 indicates receive activity on any of its 4 twisted pair ports by asserting the local activity output (LACTOUT_N). The LACTOUT_N signals from each NWK954 connect to the local activity inputs (LACTIN_N) of all the other cascaded NWK954s.

When a collision occurs between 2 twisted pair ports on an NWK954, the event is communicated to other cascaded NWK954s by asserting the collision signal (BPCOL_N). This instructs all cascaded NWK954s to transmit the jam signal for the duration of the collision event. BPCOL_N is also asserted when a collision occurs between 2 twisted pair ports on different NWK954s.

Backplane

The Expansion Port allows hubs to be stacked via a backplane bus. This requires the addition of some simple external driver/ receivers. The functional requirement for these components is illustrated in Fig. 6. Contact Mitel for full details of recommended components.

	NWK954
BPACTIN_ N [7:1]
5
LACTIN_N [5:1]
LACTOUT_N
BPCOLIN_N	TXCLKIN
BPCOL_N
BPCLK
5
IRD [4:0]
BPACTIN_ N [7:1]
5
LACTIN_N [5:1]
LACTOUT_N
BPCOLIN_N	TXCLKIN
BPCOL_N
BPCLK
5
IRD [4:0]
BPACTIN_ N [7:1]
5
LACTIN_N [5:1]
LACTOUT_N
BPCOLIN_N	TXCLKIN
BPCOL_N
BPCLK
5
IRD [4:0]
BPACTIN_ N [7:1]
5
LACTIN_N [5:1]
LACTOUT_N
BPCOLIN_N	TXCLKIN
BPCOL_N
BPCLK
5
IRD [4:0]
BPACTIN_ N [7:1]
5
LACTIN_N [5:1]
LACTOUT_N
BPCOLIN_N	TXCLKIN
BPCOL_N
BPCLK
5
IRD [4:0]
BPACTIN_ N [7:1]
5
LACTIN_N [5:1]
LACTOUT_N
BPCOLIN_N	TXCLKIN
BPCOL_N
BPCLK
5
IRD [4:0]
	CLOCK
	DRIVER
	25MHz
	OSCILLATOR

Fig. 5 Cascaded NWK954s

5