adm6995 ETC-unknow, adm6995 Datasheet - Page 24

• Manufacturer Part Number: adm6995
• Description: Port 10/100 Mb/s Single Chip Ethiernet Switch Controller
• Manufacturer: ETC-unknow

ADM6995L
ADMtek Inc.
3.9
3.10 Automatic Link Polarity Detection
3.11 Clock Synthesizer
3.12 Auto Negotiation
24ms, the 10Base-T transmitter will be disabled. Once disabled by the jabber function,
the transmitter stays disabled for the entire time that the TXEN signal is asserted. This
signal has to be de-asserted for approximately 256 ms (The un-jab time) before the jabber
function re-enables the transmit outputs. The jabber function can be disabled by
programming bit 4 of register address 10h to high.
Link Test Function
A link pulse is used to check he integrity of the connection with the remote end. If valid
link pulses are not received, the link detector disables the 10Base-T twisted-pair
transmitter, receiver, and collision detection functions.
The link pulse generator produces pulses as defined in IEEE 802.3 10Base-T standard.
Each link pulse is nominally 100ns in duration and is transmitted every 16 ms, in the
absence of transmit data.
ADM6995L’s 10Base-T transceiver module incorporates an “automatic link polarity
detection circuit”. The inverted polarity is determined when seven consecutive link pulses
of inverted polarity or three consecutive packets are received with inverted end-of-packet
pulses. If the input polarity is reversed, the error condition will be automatically corrected
and reported in bit 5 of register 10h.
The ADM6995L implements a clock synthesizer that generates all the reference clocks
needed from a single external frequency source. The clock source must be a TTL level
signal at 25 MHz +/- 50ppm
The Auto Negotiation function provides a mechanism for exchanging configuration
information between two ends of a link segment and automatically selecting the highest
performance mode of operation supported by both devices. Fast Link Pulse (FLP) Bursts
provide the signaling used to communicate auto negotiation abilities between two devices
at each end of a link segment. For further detail regarding auto negotiation, refer to
Clause 28 of the IEEE 802.3u specification. The ADM6995L supports four different
Ethernet protocols, so the inclusion of auto negotiation ensures that the highest
performance protocol will be selected based on the ability of the link partner.
• 100Base-TX full duplex (highest priority)
• 100Base-TX half duplex
• 10Base-T full duplex
• 10Base-T half duplex (lowest priority)
Highest priority relative to the following list:
Function Description
3-8