TLK110 Datasheet, PDF (21/104 Pages) Texas Instruments – Industrial Temp, Single Port 10/100Mbs Ethernet Physical Layer

TLK110
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SLLS901A – DECEMBER 2011 – REVISED FEBRUARY 2012
The RMII specification has the following characteristics:
• It is capable of supporting 10Mb/s and 100Mb/s data rates
• A single clock reference is sourced from the MAC to PHY (or from an external source)
• It provides independent 2 bit wide (di-bit) transmit and receive data paths
• It uses TTL signal levels, compatible with common digital CMOS ASIC processes
In this mode, data is transferred two bits at a time using the 50MHz RMII_REF clock for both transmit and
receive. The following pins are used in the RMII mode:
Signal
Pin
XI (RMII reference clock is 50MHz)
34
TXD_0
3
TXD_1
4
TX_EN
2
CRS_DV
40
RX_ER
41
RXD_0
43
RXD_1
44
Data on TXD [1:0] are latched at the PHY with reference to the reference-clock edges on the XI pin. Data
on RXD [1:0] are latched at the MAC with reference to the same reference clock edges on the XI pin. The
RMII operates at the same speed (50 MHz) in both 10B-T and 100B-TX. In 10B-T the data is 10 times
slower than the reference clock, so transmit data is sampled every 10 clocks. Likewise, receive data is
generated on every 10th clock so that an attached MAC device can sample the data every 10 clocks.
In addition, RMII mode supplies an RX_DV signal which allows a simpler method of recovering receive
data without the need to separate RX_DV from the CRS_DV indication. RMII mode requires a 50MHz
oscillator to be connected to the device XI pin.
The TLK110 supports a special mode called “RMII receive clock” mode. This mode, which is not part of
RMII specification, allows synchronization of the MAC-PHY RX interface. In this mode, the PHY generates
a recovered 50Mhz clock through the RX_CLK pin and synchronizes the RXD[1:0], CRS_DV, RX_DV and
RX_ER signals to this clock. Setting register 0x000A bit [0] is required to activate this mode.
Figure 4-2 describes the RMII signals connectivity between the TLK110 and any MAC device.
Copyright © 2011–2012, Texas Instruments Incorporated
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