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LXT9860/9880
—
Advanced 10/100 Repeater with Integrated Management
26
Datasheet
Document #: 248987
Revision#: 003
Rev Date: 08/07/01
Table 7. Serial Management Interface Signal Descriptions
Pin
Symbol
Type
1, 2,
Description
57
RECONFIG
I
PD
Reconfigure
. This input determines whether SERCLK is an input
or an output. When RECONFIG is High, the LXT98x0 drives
SERCLK with a 625 kHz output. When RECONFIG is Low,
SERCLK is an input to the LXT98x0. If the LXT98x0 detects a
Low-to-High transition on RECONFIG, or if RECONFIG is High at
power-up, it sends out a
“
Configuration Change
”
message (Start
Flag with all 0s) on the bus.
63
SER_MATCH
O
Serial Match.
The LXT98x0 device with Chip ID = 00 asserts this
active High output whenever it detects a message on the SMI
matching the local Hub ID. See
“
Serial Management I/F
”
on
page 52.
58
SRX
I
PD
Serial Receive.
Receive data input for SMI. Must be tied to STX
externally. SRX is sampled on the rising edge of SERCLK.
59
STX
O
OD
Serial Transmit.
Transmit data output for SMI. Must be tied to
SRX externally. Data transmitted on STX is compared with data
received on SRX. In the event of a mismatch, STX goes to a high
impedance state. STX is driven on the falling edge of SERCLK.
60
SERCLK
I/O
Tri-state
PD
Serial Clock.
Clock for SMI. Depending on RECONFIG, this pin
is either a 625 kHz output or a 0 to 2 MHz input.
198
ARBIN
I
PD
Arbitration In/Out
. Used with Chain Arbitration. If used, tie
ARBIN to ARBOUT of the previous device. ARBIN at the top of
the daisy chain can be connected to ground or to ARBOUT of the
SCC. If unused, tie ARBIN High.
65
ARBOUT
O
186
ARBSELECT
I
3
O - OD/OS
Arbitration Mode Select -
Input.
0 = PROM based, 1 = chain based.
This configuration pin also functions as the COL100 LED output
(refer to Note 3 below and to
Table 8
).
67
MGR_PRES
I
PU
Manager Present.
This signal is sensed at power up, hardware
reset, and software reset. If the signal is High, it indicates no local
manager is present, and the LXT98x0 enables all ports and sets
all LEDs to operate in
“
hardware mode
”
. If it is Low, indicating a
manager is present, the LXT98x0 disables all ports, pending
control of network manager.
1. I = Input, O = Output, I/O = Input/Output, D = Digital, A = Analog, AI = Analog Input,
A I/O = Analog Input/Output, OD = Open Drain, OS = Open Source, PD = Pull Down, PU = Pull Up.
NC = No Clamp. Pad does not clamp input in the absence of power.
2. Pins are 5V tolerant, unless indicated.
3. Input must be static. Refer to
“
LED Pins Multiplexed with Configuration Inputs
”
on page 69
for information
on pin use.