MDS212 Datasheet, PDF (44/111 Pages) Zarlink Semiconductor Inc – 12-Port 10/100Mbps Ethernet Switch

CPU Bus
MDS212
Data Sheet
31
24 23
16 15
87
0
Byte 0
Byte 1
Byte 2
Byte 3
31
24 23
16 15
87
0
Internal Data Bus
Byte 3
Byte 2
Byte 1
Byte 0
11.0 The LED Interface
Figure 14 - An example of byte swapping
11.1 LED Interface
The MDS212 LED interface supports the status per port in a serial stream that may be daisy-chained to connect
two MDS212 chips. Daisy-chaining greatly reduces the pin count and number of board traces routed from the
Physical Layer to the LEDs, thus simplifying system design and reducing overall system cost. For a large port
configuration such as the 24 in the MDS212, a large number of LED signals is needed, which may induce noise and
layout issues in the system. The LED information is transmitted in a frame-structured format with a synchronization
pulse at the start of each frame.
MDS212
Master
LE_SYNCO
LE_DO
LE_SYNCI
LE_DI
MDS212
Slave
LE_CLKO
LE_SYNCO
LE_DO
LED
Decoder
LED Display
Figure 15 - LED Interface Connections
To provide the port status information from our MDS212 chips via a serial output channel, five additional
pins are required.
• LE_CLKO - at 12.5 MHz
• LE_SYNCI/O - a sync pulse -- defines the boundary between frames
• LE_DI/O - acontinuous serial stream of data for all status LEDs which repeat once every frame time
A low cost external device (i.e. a 44-pin FPGA-like device) decodes the LED framed data and drives the LED array
for display. This device may be customized for different system configurations.
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Zarlink Semiconductor Inc.