
LXT9860/9880
—
Advanced 10/100 Repeater with Integrated Management
58
Datasheet
Document #: 248987
Revision#: 003
Rev Date: 08/07/01
3.10.3.1
Chain Arbitration Mechanism
The chain method is the easiest and requires no serial PROM. The ARBSELECT pin on all devices
must be set to 1. When constructing the stack, the designer creates a daisy chain by tying the
ARBOUT pin of each LXT98x0 to the ARBIN pin of the following LXT98x0. The manager is at
the top of the stack and controls the ARBIN for the first LXT98x0. The manager progressively
assigns Hub IDs using the Assign Hub ID (Arb Method 2) and Set ARBOUT to ZERO commands.
The manager initially sets its ARBOUT (first LXT98x0
’
s ARBIN) to zero. Since the Assign Hub
ID (Arb Method 2) command only works on the LXT98x0 with ARBIN of 0 and an ARBOUT of
1, the first LXT98x0 can be assigned an address. After the first LXT98x0 has been assigned an
address, it can uniquely be told to switch its ARBOUT to zero. This creates the (01) condition on
the next LXT98x0 in the line. This LXT98x0 is then assigned an address and the process continues
until all chips have been assigned a unique address.
Note:
It is recommended that HubIDs match in any given hub.
The manager can verify that a hub is still present by performing DEVICE ID commands. If a
change of configuration is detected, the manager can perform a broadcast write to return each hub
’
s
ARBOUT to 1, and then re-perform the address assignment process.
When using the chain arbitration method, set up the daisy chain so the device with ChipID = 00 is
the first device in the board that the chain passes through. When assigning IDs, the
‘
1st in Chain
’
bit in the device revision register (refer to
Table 77 on page 111
) can be used to determine when a
new board has been encountered.
3.10.3.2
PROM Arbitration Mechanism
This mechanism requires one serial PROM with a unique 48-bit ID in each board. This ID can
consist of serial number, date/week/year of manufacture, etc. The ARBSELECT pin must be set to
0. At power-up, the device with ChipID = 00 reads a 48-bit ID from the PROM. All other devices
Figure 15. Address Arbitration Mechanisms
1
LXT98x0
ARBIN
ARBOUT
Network
Manager
ARBOUT
Serial I/F to Next Module
SRX/STX
LXT98x0
ARBIN
ARBOUT
SRX/STX
0
SRX/STX
Hub Board 1
1
LXT98x0
ARBIN
ARBOUT
SRX/STX
1
LXT98x0
ARBIN
ARBOUT
SRX/STX
0
Hub Board 2
ARBI/O Chain to Next Module
0
Chain Mechanism for
Address Arbitration
Network
Manager
Serial I/F to Next Module
SRX/STX
Hub Board 1
Serial
EPROM
LXT98x0
SRX/STX
PROMDTI/O
LXT98x0
SRX/STX
PROMDTI/O
Hub Board 2
Serial
EPROM
LXT980
SRX/STX
PROMDTI/O
LXT980
SRX/STX
PROMDTI/O
EPROM Mechanism
for Address Arbitration