adm6996f Infineon Technologies Corporation, adm6996f Datasheet - Page 24

• Manufacturer Part Number: adm6996f
• Description: 6 Port 10/100 Mb/s Single Chip Ethernet Switch Controller
• Manufacturer: Infineon Technologies Corporation

ADM6996F
Infineon-ADMtek Co Ltd.
3.6.1 Operation Modes
3.6.2 Manchester Encoder/Decoder
3.6.3 Transmit Driver and Receiver
3.6.4 Smart Squelch
functions, as defined in the standard. Figure 3 provides an overview for the 10Base-T
module.
The ADM6996F 10Base-T module is comprised of the following functional blocks:
x Manchester encoder and decoder
x Collision detector
x Link test function
x Transmit driver and receiver
x Serial and parallel interface
x Jabber and SQE test functions
x Polarity detection and correction
The ADM6996F 10Base-T module is capable of operating in either half-duplex mode or
full-duplex mode. In half-duplex mode, the ADM6996F functions as an IEEE 802.3
compliant transceiver with fully integrated filtering. The COL signal is asserted during
collisions or jabber events, and the CRS signal is asserted during transmit and receive. In
full duplex mode the ADM6996F can simultaneously transmit and receive data.
Data encoding and transmission begins when the transmission enable input (TXEN) goes
high and continues as long as the transceiver is in good link state. Transmission ends
when the transmission enable input goes low. The last transition occurs at the center of
the bit cell if the last bit is a 1, or at the boundary of the bit cell if the last bit is 0.
Decoding is accomplished by a differential input receiver circuit and a phase-locked loop
that separate the Manchester-encoded data stream into clock signals and NRZ data. The
decoder detects the end of a frame when no more mid bit transitions are detected. Within
one and half bit times after the last bit, carrier sense is de-asserted.
The ADM6996F integrates all the required signal conditioning functions in its 10Base-T
block such that external filters are not required. Only one isolation transformer and
impedance matching resistors are needed for the 10Base-T transmit and receive interface.
The internal transmit filtering ensures that all the harmonics in the transmission signal are
attenuated properly.
The smart squelch circuit is responsible for determining when valid data is present on the
differential receive. The ADM6996F implements an intelligent receive squelch on the
RXP/RXN differential inputs to ensure that impulse noise on the receive inputs will not
be mistaken for a valid signal. The squelch circuitry employs a combination of amplitude
Function Description
3-6