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82555 — Networking Silicon
Twisted Pair Ethernet (TPE) receiver is greater than 585 mV and less than 3.1 V. The TPE receive
buffer distinguishes valid receive data, link test pulses, and the idle condition, according to the
requirements of the 10BASE-T standard.
The following line activity is determined to be inactive and is rejected:
•
Differential pulses of peak magnitude less than 300 mV.
•
Continuous sinusoids with a differential amplitude less than 6.2 V
MHz.
•
Sine waves of a single cycle duration starting with 0° or 180° phase that have a differential
amplitude less than 6.2 V
These single-cycle sine waves are discarded only if they are preceded by 4 bit times (400
nanoseconds) of silence.
All other activity is determined to be either data, link test pulses, Auto-Negotiation fast link pulses,
or the idle condition. When activity is detected, the carrier sense signal is asserted to the MAC.
5.3.3
10BASE-T Error Detection and Reporting
In 10 Mbps mode, the 82555 can detect errors in the receive data. The following condition is
considered an error:
The receive pair's voltage level drops to the idle state during reception before the end-of-frame
bit is detected (250 nanoseconds without mid-bit transitions).
5.4
10BASE-T Collision Detection
Collision detection in 10 Mbps mode is indicated by simultaneous transmission and reception. If
the 82555 detects this condition, it asserts a collision indication to the controller.
5.5
10BASE-T Link Integrity
The link integrity in 10 Mbps works with link pulses. The 82555 senses and differentiates those
link pulses from fast link pulses and from 100BASE-TX idles. In the first and last case, the 82555
activates parallel detection of the respective technology; and in the second case, Auto-Negotiation.
The 10 Mbps link pulses or normal link pulses are driven in the transmit differential pair line but
are 100 ns wide and have levels from 0 V to 5 V. The link beat pulse is also used to determine if the
receive pair polarity is reversed. If it is, the polarity is corrected internally.
5.6
10BASE-T Jabber Control Function
The 82555 contains a jabber control function that inhibits transmission after a specified time
window when enabled. In 10 Mbps mode, the jabber timer is set to a value between 26.2 ms and 39
ms. If the 82555 detects continuous transmission that is greater than this time period, it prevents
further transmissions from onto the wire until it detects that the MAC transmit enable signal has
been inactive for at least 314 ms.
22
and a frequency of at least 2 MHz and not more than 16 MHz.
pp
and frequency less than 2
pp
Datasheet
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