78Q2120C09-CGTR/F Maxim Integrated Products, 78Q2120C09-CGTR/F Datasheet - Page 5

• Manufacturer Part Number: 78Q2120C09-CGTR/F
• Description: Telecom ICs 10-100 Fast Ethernet Transceiver Twisted
• Manufacturer: Maxim Integrated Products

Specifications of 78Q2120C09-CGTR/F

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Station Management Interface
The station management interface consists of
circuitry which implements the serial protocol as
described in Clause 22.2.4.5 of IEEE-802.3. A 16-
bit shift register receives serial data applied to the
MDIO pin at the rising-edge of the MDC clock signal.
Once
management control logic looks for the start-of-
frame sequence and a read or write op-code,
followed by the PHYAD and REGAD fields. For a
read operation, the MDIO port becomes enabled as
an output and the register data is loaded into a shift
register for transmission. The 78Q2120C can work
with a one bit preamble rather than the 32 bits
prescribed by IEEE-802.3.
programming of the registers. If a register does not
exist at an address indicated by the REGAD field or
if the PHYAD field does not match the 78Q2120C
PHYAD indicated by the PHYAD pins, a read of the
MDIO port will return all ones. For a write operation,
the data is shifted in and loaded into the appropriate
register after the sixteenth data bit has been
received.
When the PHYAD field is all zeros, the Station
Management Entity (STA) is requesting a broadcast
data transaction.
Management
broadcast request. The 78Q2120C will respond to
the broadcast data transaction.
ADDITIONAL FEATURES
LED Indicators
There are seven LED pins that can be used to
indicate
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the preamble
various
Interface
states
All PHYs sharing the same
is
must
of
received, the
This allows for faster
operation
respond
©
2009 Teridian Semiconductor Corporation
to
of
station
this
the
78Q2120C. There is an LED pin that indicates the
link is up (LEDL), others that indicate the 78Q2120C
is either transmitting (LEDTX) or receiving (LEDRX),
one that signals a collision event (LEDCOL), two
more that reflect the data rate (LEDBTX and LEDBT),
and one that reflects full duplex mode of operation
(LEDFDX).
Interrupt Pin
The 78Q2120C has an Interrupt pin (INTR) that is
asserted whenever any of the eight interrupt bits of
MR17.7:0 are set.
disabled via the MR17.15:8 Interrupt Enable bits.
The Interrupt Polarity bit, MR16.14, controls the
active level of the INTR pin. When the INTR pin is
not asserted, this pin is held in a high impedance
state. An external pull-up or pull-down resistor may
be required for use with the INTR pin.
APPLICATIONS REQUIREMENTS
RXIP/N Termination Connection
The input circuitry of the TERIDIAN 78Q2120C has
changed for continuing performance improvements.
Device revision C09 requires that the RXIP/N
termination resistors and transformer center tap
connections be directly connected to VCC for proper
receiver operation.
Applications Circuit for the schematic showing the
required
transformer center tap connections to VCC for
revision 78Q2120C.
RXIP/N
These interrupt bits can be
termination
Refer to Figure 1: Typical
10/100BASE-TX
Transceiver
resistors
78Q2120C
Rev 1.3
and