5228-DS07-R datasheet(42/100 Pages) BOARDCOM

42 / 100 page

BCM5228

Data Sheet

7/12/04

Broa d c om Co rp o r a t i o n

Page 30

Low-Cost Serial LED Mode

Document

5228-DS09-405-R

LOW-COST SERIAL LED MODE

The low-cost serial LED mode is enabled by pulling both LC_SER_EN pin and SER_EN pin high during power-on reset.

When enabled, serial LED data stream, SLED_DO, is shifted out on the falling edge of SLED_CLK. SLED_DO is valid on

the rising edge of this clock. The data is shifted in such a manner that the update of LEDs using a simple shift register that

drive the display LEDs do not cause noticeable flicker in normal operation.

There are six banks, bank 1 through bank 6, associated with six LED outputs. Each bank has its own MII register bits that

select LED a signal to output from that bank. The selected signal from each bank is shifted out on the LED_DO pin in the

following order for a total of 48 LED outputs:

•

Bank 1 for port 1 through port 8

•

Bank 2 for port 1 through port 8,…,

•

Bank 6 for port 1 through 8

The low-cost serial LED mode programmable banks are located in the MII shadow register 1Ah of port 2 and port 3. For

programming details, see Table 7, Table 8, Table 9, Table 10, Table 11, and Table 12. The default LED outputs are Speed,

Link, Full-duplex, Activity, Speed, and Link for bank 1 through bank 6, respectively.

Table 7: Low-Cost Serial Mode Bank 1 LED Selection

MII Shadow Registera 1Ah, PHY 3, Bits [2:0]

a. The MII Shadow register is accessed by setting MII register 1Fh bit 7 to 1.

Value

LED Selection

SERIAL BANK 1 SELECT

BITS[2:0]

Speed

Activity

Full-duplex

3Transmit

Receive

Interrupt

Collision

7Link

Table 8: Low-Cost Serial Mode Bank 2 LED Selection

MII Shadow Registera 1Ah, PHY 3, Bits [5:3]

a. The MII Shadow register is accessed by setting MII register 1Fh bit 7 to 1.

Value

LED Selection

SERIAL LED BANK 2 SELECT

BITS[2:0]

0Link

Speed

Activity

Full-duplex

4Transmit

Receive

Interrupt

7Collision

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