4.9.3. SFP+ Interface
Two SFP+ connectors (J5, J6) are provided on the PCIe* bracket. Each connector supports a 10 GE SFP+ hot pluggable module.
- Transceivers, x1 for each SFP+, up to 12.5 Gbps
- SMBUS (I2C), 3.3V for SFP+ and I/O expander, level-translated 10 1.8V with U22/U23
- IRQ of I/O expander, 3.3V level-translated to 1.8V with U19
Each SFP+ module has six status/control signals and two LEDs. The FPGA device does not have enough I/O pins for these signals, hence an I/O expander is used to implement these I/Os for each SFP+ connector. The I2C I/O expander is on the same I2C bus as the SFP+ module, and the I2C bus of two SFP+ modules are independent of each other.
The I/O expander used is TI TCA9534PWR. U20 is for SFP+ 0, with I2C address 7'b010_0000. U21 is for SFP+, with I2C address 7'b010_0000.
The I/O expander has 8 I/Os. The definition of the I/Os is shown in the table below. The device is controlled with I2C bus.
|I/O Number||Signal||I/O Type||Function|
|P0||SFP_RLED||Output||Red LED, indicates LOS/ERR, "0" - ON|
|P1||SFP_GLED||Output||Green LED, indicates Link, "0" - ON|
|P2||SFP_TXDIS||Output||Tx_Disable, Pulled up, Transmitter is turned off if high|
|P3||SFP_TFLT||Input||Tx_Fault, Pulled up, indicates fault when high|
|P4||SFP_RS1||Output||Rate Select, Pulled up with 1K resistor|
|P5||SFP_RLOS||Input||Rx_LOS, Pulled up, indicates LOS when high|
|P6||SFP_RS0||Output||Rate Select, Pulled up with 1K resistor|
|P7||SFP_PRSN||Input||Mod_ABS, Pulled up, module in place when low|
The I/Os of TCA9534 is in high impedance input mode upon power up. Hence, the module is placed in TX_Disable mode and the LEDs are off. The status changes on the I/Os are reported with an IRQ to the FPGA. Each I/O expander has its own dedicated IRQ signal.
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