As shown in the following figure, the card uses a combination of I2C multiplexers (PCA9545A) and I/O expanders (TCA6408A) to access and control power and sideband signals for all four QSFP56 modules. The sideband signals include:
- LPMODE
- INTR
- MODPRSL
- MODSELL
- RESETL
The power signals include:
- QSFP_EN (power enable)
- QSFP_PG (power good)
The other QSFP56 I/O expanders have identical sideband signals but are not explicitly shown. To access/control particular QSFP56 signals requires enabling a particular combination of I2C multiplexers and I/O expanders.
Figure 1. QSFP56 I2C Logic
