Cabletron Systems MICROMMAC-22T Active TCU Ports, Cable Signal Polarity, Speed Fault Protection

INTRODUCTION

Active TCU Ports

The active TCU ports regenerate, reshape, and filter the incoming signal, permitting UTP lobe cable lengths of up to 120 meters and STP lobe cable lengths up to 150 meters at 16 Mbps ring speed. The MicroMMAC-22T and the MicroMMAC-42T can be upgraded in the field using the Cabletron UTP and STP 12-port upgrade kits.

Cable Signal Polarity

Differential Manchester encoding is used for each concentrator module TCU port. This permits passing data regardless of receive link polarity.

NOTE: The MicroMMAC-T is not affected by the reversed polarity condition. If, however, such a condition is discovered, the segment should be removed from the network and wired correctly to avoid problems during future network operations. Refer to Section 3.8 for cable pinouts specifications

Speed Fault Protection

If a station attempts to insert into a ring port at a different speed from the one set on the MicroMMAC-T, that port is automatically bypassed to prevent the ring from beaconing. The Lobe Port Status LED blinks red (for more information, see Section 5.1, USING LANVIEW LEDs) to indicate that the port with the speed fault is being bypassed.

Local Management

Local Management provides you with the ability to manage the MicroMMAC-T and all of its attached segments, including most BRIMs and the MicroSNAC device. The CR BRIM-W/T and the MicroSNAC provide their own configuration firmware.

Access Local Management by connecting an actual or emulated Digital Equipment Corporation VT100™ series terminal to the MicroMMAC-T’s COM 1 port or the COM 2 port. To view diagnostic test information from a display terminal, use the COM 2 port.

Token Ring Port Interface Modules (TPIMs)

TPIMs are modular connector cards used for expanding trunk connections to a range of Token Ring media. TPIMs have embedded repeaters that

1-4