FWLXT9784BC.A3 Cortina Systems Inc, FWLXT9784BC.A3 Datasheet - Page 41

• Manufacturer Part Number: FWLXT9784BC.A3
• Manufacturer: Cortina Systems Inc

Specifications of FWLXT9784BC.A3

• Lead Free Status / RoHS Status: Not Compliant

2.6.5
2.7
2.8
Datasheet
Table 16. PHY Addresses
The BP4B5B pin and bit 14 in PHY register 11’h are ORed together. This pin bypasses the 4B5B
encoder/decoder in the transmit and receive sections. In 4B5B bypass mode the data is transmitted
in 5-bit symbols. In RMII mode, the fifth bit (MSB) of all eight ports is driven through the TXD4
pin. The TXD4 pin is a static pin and should be pulled up or pulled down. In SMII mode, TXER
represents the fifth bit.
SCRMBP
In order to enter scrambler by-pass this pin must be set high after the end of reset. During reset this
pin must be pulled-down to ensure proper operation of the LXT9784.
The SCRMBP pin and bit 15 in PHY register 11'h are ORed together.
PHY Addresses
The ID<1:0> pins are used to set the PHY addresses for the MII management interface.
The PHYs are assigned consecutive addresses in increasing order, starting with PHY0. The address
of PHY0 is determined by the setting of ID<1:0>. This allows up to
four LXT9784s to be connected on a single MII management bus. Up to thirty-two ports are
available when using all the combinations of ID<1:0>.
for each of the possible combinations of ID<1:0>.
Link Status Interrupt
The LXT9784 provides an open-drain interrupt pin (INT), which is driven low by the LXT9784
when one or more of it’s internal PHYs has a change in link status.
diagram of the interrupt structure.
When INT is driven low, all of the PHY interrupt registers should be read, to determine which port
or ports caused the interrupt (Refer to Table 51). Once a PHY interrupt bit has been read, it is self-
cleared. The interrupt line becomes inactive only after reading the Link Status Interrupt bits of all
the PHYs that caused the interrupt. In the case of more than one PHY having an interrupt pending,
INT remains asserted until after reading the last PHY with a Link Status Interrupt bit set to “1”.
If during the procedure of reading the interrupt registers a new change of link status occurred on a
PHY which has already been accessed, the interrupt line remains asserted after completing the read
procedure.
This feature can be used instead of polling the PHYs for link status change.
ID_1
0
0
1
1
ID_0
0
1
0
1
(Scrambler Bypass)
00000
01000
10000
11000
PHY0
00001
01001
10001
11001
PHY1
00010
01010
10010
PHY2
11010
PHY3
00011
01011
10011
11011
Table 16
Low-Power Octal PHY — LXT9784
00100
01100
10100
PHY4
11100
shows the internal PHY addresses
Figure 11
00101
01101
10101
PHY5
11101
is a simplified
00110
01110
10110
PHY6
11110
PHY7
00111
10111
01111
11111
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