DS80PCI102_15 Datasheet, PDF (15/46 Pages) Texas Instruments – 2.5-Gbps / 5.0-Gbps / 8.0-Gbps 1-Lane PCI-Express Repeater With Equalization and De-Emphasis

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DS80PCI102
SNLS344G – JULY 2011 – REVISED AUGUST 2015
7.4 Device Functional Modes
The DS80PCI102 is a low power media compensation 1 lane repeater optimized for PCI Express Gen 1/2 and 3.
The DS80PCI102 compensates for lossy FR-4 printed circuit board backplanes and balanced cables. The
DS80PCI102 operates in 3 modes: Pin Control Mode (ENSMB = 0), SMBus Slave Mode (ENSMB = 1) and
SMBus Master Mode (ENSMB = float) to load register information from external EEPROM; refer to Table 8 for
additional information.
7.4.1 Pin Control Mode
When in pin mode (ENSMB = 0), equalization and de-emphasis can be selected through pin for each side
independently. When de-emphasis is asserted VOD is automatically adjusted per the De- Emphasis table below.
The RXDET pins provides automatic and manual control for input termination (50 Ω or > 50 kΩ). RATE setting is
also pin controllable with pin selections (Gen 1/2, auto detect and Gen 3). The receiver electrical idle detect
threshold is also adjustable through the SD_TH pin.
7.4.2 SMBUS Mode
When in SMBus mode (ENSMB = 1), the VOD (output amplitude), equalization, de-emphasis, and termination
disable features are all programmable on a individual lane basis, instead of grouped by A or B as in the pin mode
case. Upon assertion of ENSMB, the EQx and DEMx functions revert to register control immediately. The EQx
and DEMx pins are converted to AD0-AD3 SMBus address inputs. The other external control pins (RATE,
RXDET and SD_TH) remain active unless their respective registers are written to and the appropriate override bit
is set, in which case they are ignored until ENSMB is driven low (pin mode). On power-up and when ENSMB is
driven low all registers are reset to their default state. If PRSNT is asserted while ENSMB is high, the registers
retain their current state.
Equalization settings accessible through the pin controls were chosen to meet the needs of most PCIe
applications. If additional fine tuning or adjustment is needed, additional equalization settings can be accessed
through the SMBus registers. Each input has a total of 256 possible equalization settings. The 4-Level Input
Configuration Guidelines show the 16 setting when the device is in pin mode. When using SMBus mode, the
equalization, VOD and de-emphasis levels are set by registers.
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