ADM7008
Function Description
3.1.15 Automatic Link Polarity Detection
ADM7008’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 13 of register 11h.
3.1.16 Clock Synthesizer
The ADM7008 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.
3.1.17 Cable Broken Auto Detection
The Cable Broken Auto Detection Feature uses Time Domain Reflectometry (TDR) to
determine if the cable opens. The TDR test can be performed when the ADM7008 is
Auto-Negotiating or sending 10Mbit idle link pulses. After power on reset, the
ADM7008 transmits link pulses down the pair of an attached cable continuously. The
magnitude of the reflection and the time it takes for the reflection to come back are
recorded. Using the recorded information, the cable status and the distance to the broken
location can be determined and are shown in register22.13 and 22.12:11 respectively. If
the cable properly terminated there will be no reflections. If there are no reflections it will
declare the cable is connected properly. If medium detect function is turn on and the
received signal is detected. MD in register 22:10 is “1”, it will also declare the cable is
not broken. If the cable is connection properly, the cable length can be determined by
DSP algorithms at 100M good link state and as indicated in register 22.7:0.
ADMtek Inc.
3-11
ETC [ ETC ]
