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ICS1890
Carrier Detector
In half duplex mode carrier is asserted during transmission or
reception of data. In full duplex or repeater mode, carrier is
asserted only on reception of data.
Collision Detector
Collision occurs whenever there is simultaneous transmit
and receive activity when a half duplex link is established.
Collision never occurs in full duplex mode.
Jabber
The Jabber function prevents the transmitter from erroneously
transmitting for too long a period. The maximum time the
device should transmit continuously is the time it takes to
send a maximum length packet (1500 bytes). The Jabber
function ensures that transmission lasts no longer than 20-
150ms. The typical value for the ICS1890 is 21ms.
When the jabber timer is exceeded, Collision (COL) is
asserted and the transmit output goes idle for 0.5 ±0.25s.
This function can be disabled with the Jabber Inhibit register
bit (18:5).
SQETest
This test is only used in Half Duplex DTE applications and is
disabled in repeater and Full Duplex mode. This test can also
be disabled with the SQE Test Inhibit register bit (18:2).
When enabled and a link is established, 0.6 to 1.6us after the
last positive transition of a transmitted packet, COL will be
asserted for 10 ±5 bit times.
Manchester Encoder/Decoder
When the ICS1890 is operating in the 10Base-T mode,
Manchester coding is used. When transmitting nibbles from
the MII are converted to a serial bit stream and then Manchester
en-coded. When receiving, the Manchester encoded bit stream
is decoded and converted to nibbles for presentation to the
MH.
Clock Synthesis
A 2.5MHz clock is synthesized for nibble wide transactions.
A 10MHz clock is synthesized for serial transactions.
Clock Recovery
The PLL synchronizes on the MAC fram preamble and then
begins recovering data normally.
Squelch
The squelch function qualifies the data coming into the device
so that spurious noise events are rejected.
Auto Polarity Correction
By examining the polarity of received Link Pulses theICS1890
can determine if the two wires in the receive data pair were
wired correctly. If the wires were accidentally reversed during
installation, the Auto Polarity Correction function can
automatically correct this in the ICS1890. If the ICS1890
corrects the polarity, this is reflected in the 10Base-TOperations
register. This function can also be disabled through the same
register, if desired.
Line Transmitter
The line transmitter logic of the ICS1890 is a current-driven
differential driver which can be programmed for either two-
level(10Base-T,Manchester)orthree-level(100Base-TX,MLT-
3) transmission. Wavespaping is applied to control the output
edge late and eliminate the need for expensive external filters.
The transmitter interfaces directly to an inexpensive isolation
transformer (magnetics).
Line Receiver
The line receiver circuit accepts either a differential two-level
(10Base-T, Manchester) or three-level (100Base-TX, MLT-3)
signal which first passes through an isolation transformer. If
the polarity correct bit in the Configuration Register is asserted,
the ICS1890 will sense the polarity of the receive pair and, if
necessary, switch polarity automatically.
Magnetics
A Universal Magnetics module is used to provide isolation
and signal coupling onto the twisted pair cabling for both
10Base-T and 100Base-TX.