DS125RT410_15 Datasheet, PDF (11/58 Pages) Texas Instruments – Low-Power Multi-Rate Quad Channel Retimer

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Feature Description (continued)
1.0
DS125RT410
SNLS459A – APRIL 2013 – REVISED OCTOBER 2015
0.5
0.0
-0.5
-1.0
0 1 2 3 4 5 6 7 8 9 10
TIME (UI)
Figure 4. Idealized De-Emphasis Waveform
7.3.6 Device Configuration
The DS125RT410 can be configured by the user to optimize its operation. The four channels can be optimized
independently in SMBus master or SMBus slave mode. The operational settings available for user configuration
include the following.
• Rate and subrate setting
• Driver output voltage (refer to Driver Output Voltage)
• Driver output de-emphasis (refer to Driver Output De-Emphasis)
• Driver output rise/fall time (refer to Driver Output Rise and Fall Time)
7.3.6.1 Rate and Subrate Setting
Register 0x2f, bits 7:4, Registers 0x60, 0x61, 0x62, 0x63, and 0x64
The DS125RT410 is part of a family of retimer devices differentiated by different VCO frequency ranges. Each
device in the retimer family is designed for operation in specific frequency bands and with specific data rate
standards.
The DS125RT410 is designed to lock rapidly to any valid signal present at its inputs. It is also designed to detect
incorrect lock conditions which can arise when the input data signals are strongly periodic. This condition is
referred to as false lock. The DS125RT410 discriminates against false lock by using its 25-MHz reference to
ensure that the VCO frequency resulting from its internal phase-locking process is correct.
To determine the correct VCO frequency, the digital circuitry in the DS125RT410 requires some user-supplied
information about the expected data rate or data rates. This information is provided by writing several device
registers using the SMBus.
7.4 Device Functional Modes
7.4.1 SMBus Master Mode and SMBus Slave Mode
In SMBus master mode the DS125RT410 reads its initial configuration from an external EEPROM upon power-
up. A description of the operation of this mode appears in the DS100DF410EVK, DS110DF410EVK,
DS125DF410EVM User's Guide (SNLU126).
Some of the pins of the DS125RT410 perform the same functions in SMBus master and SMBus slave mode.
Once the DS125RT410 has finished reading its initial configuration from the external EEPROM in SMBus master
mode it reverts to SMBus slave mode and can be further configured by an external controller over the SMBus.
The following two pins provide unique functions in SMBus master mode:
• ALL_DONE
• READ_EN
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