Pin Description
The Direct Attach Copper (DAC) pin assignment is SFF-8679 compliant.
Pin  | Symbol  | Description  | Pin  | Symbol  | Description  | 
1  | GND  | Ground  | 20  | GND  | Ground  | 
2  | Tx2n  | Transmitter Inverted Data Input  | 21  | Rx2n  | Receiver Inverted Data Output  | 
3  | Tx2p  | Transmitter Non-Inverted Data Input  | 22  | Rx2p  | Receiver Non-Inverted Data Output  | 
4  | GND  | Ground  | 23  | GND  | Grounds  | 
5  | Tx4n  | Transmitter Inverted Data Input  | 24  | Rx4n  | Receiver Inverted Data Output  | 
6  | Tx4p  | Transmitter Non-Inverted Data Input  | 25  | Rx4p  | Receiver Non-Inverted Data Output  | 
7  | GND  | Ground  | 26  | GND  | Ground  | 
8  | ModSelL  | Module Select  | 27  | ModPrsL  | Module Present  | 
9  | ResetL  | Module Reset  | 28  | IntL  | Interrupt  | 
10  | Vcc Rx  | +3.3V Power Supply Receiver  | 29  | Vcc Tx  | +3.3V Power Supply Transmitter  | 
11  | SCL  | 2-wire Serial Interface Clock  | 30  | Vcc1  | +3.3V Power Supply  | 
12  | SDA  | 2-wire Serial Interface Data  | 31  | LPMode  | Low Power Mode  | 
13  | GND  | GND  | 32  | GND  | Ground  | 
14  | Rx3p  | Receiver Non-Inverted Data Output  | 33  | Tx3p  | Transmitter Non-Inverted Data Input  | 
15  | Rx3n  | Receiver Inverted Data Output  | 34  | Tx3n  | Transmitter Inverted Data Input  | 
16  | GND  | Ground  | 35  | GND  | Ground  | 
17  | Rx1p  | Receiver Non-Inverted Data Output  | 36  | Tx1p  | Transmitter Non-Inverted Data Input  | 
18  | Rx1n  | Receiver Inverted Data Output  | 37  | Tx1n  | Transmitter Inverted Data Input  | 
19  | GND  | Ground  | 38  | GND  | Ground  | 
QSFP56 Module Pad Layout