ksz8021rnli Micrel Semiconductor, ksz8021rnli Datasheet - Page 18

• Manufacturer Part Number: ksz8021rnli
• Description: 10base-t/100base-tx Phy With Rmii Support
• Manufacturer: Micrel Semiconductor

Micrel, Inc.
Back-to-Back Mode – 100Mbps Copper Repeater / Media Converter
Two KSZ8021/31RNL devices can be connected back-to-back to form a managed 100Base-TX copper repeater.
A KSZ8021/31RNL and a KSZ8041FTL can be connected back-to-back to provide a managed media converter solution.
Media conversion is between 100Base-TX copper and 100Base-FX fiber. On the copper side, link up at 10Base-T is not
allowed, and is blocked during auto-negotiation.
RMII Back-to-Back Mode
In RMII Back-to-Back mode, a KSZ8021/31RNL interfaces with another KSZ8021/31RNL, or a KSZ8041FTL to provide a
100Mbps copper repeater, or media converter solution, respectively.
The KSZ8021/31RNL devices are configured to RMII Back-to-Back mode after they are powered up or hardware reset
and software programmed with the following:
August 2010
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A common 50MHz reference clock connected to XI (Pin 8)
Register 1Fh, bit [7] programmed to ‘1’ to select RMII – 50MHz Clock Mode for KSZ8031RNL
(KSZ8021RNL is set to RMII – 50MHz Clock Mode as the default after power up or hardware reset)
Register 16h, bits [6] and [1] programmed to ‘1’ and ‘1’, respectively, to enable RMII Back-to-Back mode.
RMII signals connected as shown in the following table.
Pin Name
CRS_DV
Table 2. RMII Signal Connection for RMII Back-to-Back Mode (100Base-TX Copper Repeater)
RXD1
RXD0
TXEN
TXD1
TXD0
KSZ8021/31RNL (100Base-TX copper)
Figure 4. KSZ8021/31RNL and KSZ8041FTL RMII Back-to-Back Media Converter
Pin Number
[Device 1]
15
12
13
19
21
20
Pin Type
Output
Output
Output
Input
Input
Input
18
Pin Name
CRS_DV
TXEN
TXD1
TXD0
RXD1
RXD0
KSZ8021/31RNL (100Base-TX copper)
Pin Number
[Device 2]
19
21
20
15
12
13
KSZ8021RNL / KSZ8031RNL
Pin Type
Output
Output
Output
Input
Input
Input
M9999-082710-1.0