10 Base T Transceiver - Functional Description
The TP MAU interfaces the attachment Unit Interface AUI to the unshielded
twisted pair cables, transferring data in both directions between the two.
The AUI side of the interface comprises of: Data Output (DO) Data Input (DI) and Control Interface (CI). The twisted pair network side of the interface comprises of: Twisted Pair Input (TPI) and Twisted Pair Output (TPO).
Transmit function.
The TP MAU transfers data from DTE AUI port DO circuit to the twisted pair
network. It is signaled by an LED.
The output signal on TPO is predistorted to meet 10 Base T jitter template
and filtered to meet FCC requirements.
During the idle periods the TP MAU transmits link integrity test pulses
on the TPO circuit.
Loopback function.
Data transmitted by the DTE is looped back from DO to DI and returned
to the DTE. Loopback function is disabled during data collision,
link fail and jabber states.
Receive function.
The TP MAU transfers data from the twisted pair network TPI to the DI
circuit of the AUI. It is signaled by an LED.
-Receiver squelch.
It discriminates noise from link test pulses and valid data streams.
The threshold can be reduced by 3dB to allow for longer loops in low noise
environments.
Polarity reverse.
A reversed polarity condition is detected and signaled by an LED when:
-eight consecutive opposite polarity receive link pulses are detected
on TPI,
-four frames are received from TPI with a reversed start-of -idle.
The polarity is automatically corrected unless it is disabled by the switch.
Collision Detection.
A "Collision" occurs when there is a simultaneous presence of valid signals
on both the TPI and TPO circuits. It is reported to the AUI over the CI
circuit and signaled by an LED.
SQE test function.
When enabled the SQE test sequence is transmitted to the AUI CI circuit
after every successful transmission on the 10 Base T network.
This function should be disabled for hub application.
Jabber Control.
When a transmission exceeds the time limit the watchdog timer disables
the transmit and loopback functions and sends the SQE signal to the DTE CI
circuit. LED is activated.
Link Integrity test.
The Link Integrity Test is used to determine status of the TPI.
When enabled the receiver recognizes the link integrity pulses which
are transmitted in absence of receive traffic. In link fail state
the transmit and loopback functions are disabled and the LED is off.
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