Technical data

ManualsBrandsSiemens ManualsSwitchERTEC200

The PHY realizes a complete 10BASE-T transceiver function. It includes the receiver, transmitter and

the following functions.

<1> Filter and squelch

<2> Jabber detection

<3> Signal quality error (SQE) message test function

<4> Timing recovery from received data

<5> Manchester encoding/decoding

<6> Full-duplex or Half-duplex mode

In half-duplex mode, the PHY transmits and simultaneously receives in order to provide

loopback of the transmitted signal. (Refer to section 14.2.1.3 of IEEE802.3 )

<7> Collision presence function (half duplex mode only)

<8> Carrier Sense Detection

CRS is asserted only to receive activity for Full-Duplex mode. CRS is asserted

during either packet transmission or reception for half-duplex mode.

(1) Filter and Squelch

The Manchester encoded signal from the cable is fed into the transceiver’s receive path via 1:1 ratio

magnetics (see Chapter

1.6.2 for details of the circuit). It is first filtered to reduce any out-of-band

noise. It then passes through a squelch circuit - a set of amplitude and timing comparators that

normally reject differential voltage levels below 300 mV and detect and recognize differential voltages

above 585 mV.

(2) Jabber detection

Jabber is a condition in which a station transmits for a period of time longer than the maximum permis-

sible packet length - usually due to a fault condition - that results in holding the TX_EN_P(2:1) signal

active for a long period. Special logic is used to detect the jabber state and to abort the transmission to

the line within 45 ms. The maximum time of of unjab is 350 ms. Once TX_EN_P(2:1) is deasserted,

the logic resets the jabber condition. Basic status register 1 indicates that a jabber condition was

detected; details about the register functions are given in Chapter

1.5.

(3) SQE test function

The PHYs on ERTEC 200 support a signal quality error (SQE) test function. This function controls if

data transmission is successful; successful transmission is indicated by activating the COL_P(2:1) sig-

nal for 1 µs, 2 µs after TX_EN_P(2:1) has been deasserted. This signal is also referred to as “heart-

beat” signal.

If desired, the SQE test function can be disabled by setting the SQEOFF bit in control/status register

27 to 1

. The setting of the SQEOFF bit is irrelevant when the PHY is working in 100BASE-TX or -FX

modes.

(4) Manchester encoding/decoding

When encoding, the 4-bit nibble data, that is coming from the MII interface, is converted to a 10 Mbps

serial NRZI data stream. The 10M PLL locks onto the external clock and produces a 20 MHz clock sig-

nal. which is used to Manchester encode the NRZ data stream.

When no data is being transmitted, normal link pulses (NLPs) are output to maintain communications

with the remote link partner.

When decoding, the 10M PLL is locked onto the received Manchester signal and from this, the internal

20 MHz receive clock is generated. Using this clock, the Manchester encoded data is extracted and

converted to a 10 MHz NRZI data stream. This stream is then converted from serial to 4-bit nibble

data.

Technical data subject to change Version 1.0.0