Pin Descriptions

QSFP28 Pin Description

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

QSFP28 Module Pad Layout

QSFP-DD Pad Description

The head end of the MCP7H60 cable has the pad assignment shown below, which is compliant with the QSFP-DD Hardware Specification ‎[2].

Pin	Symbol	Description	Pin	Symbol	Description
1	GND	Ground	39	GND	Ground
2	Tx2n	Transmitter Inverted Data Input	40	Tx6n	Transmitter Inverted Data Input
3	Tx2p	Transmitter Non-Inverted Data Input	41	Tx6p	Transmitter Non-Inverted Data Input
4	GND	Ground	42	GND	Ground
5	Tx4n	Transmitter Inverted Data Input	43	Tx8n	Transmitter Inverted Data Input
6	Tx4p	Transmitter Non-Inverted Data Input	44	Tx8p	Transmitter Non-Inverted Data Input
7	GND	Ground	45	GND	Ground
8	ModSelL	Module Select	46	Reserved
9	ResetL	Module Reset	47	VS1	Module Vendor Specific 1
10	VccRx	+3.3V Power Supply Receiver	48	VccRx1	+3.3V Power Supply Receiver
11	SCL	2-wire Serial Interface Clock	49	VS2	Module Vendor Specific 2
12	SDA	2-wire Serial Interface Data	50	VS3	Module Vendor Specific 3
13	GND	GND	51	GND	Ground
14	Rx3p	Receiver Non-Inverted Data Output	52	Rx7p	Receiver Non-Inverted Data Output
15	Rx3n	Receiver Inverted Data Output	53	Rx7n	Receiver Inverted Data Output
16	GND	Ground	54	GND	Ground
17	Rx1p	Receiver Non-Inverted Data Output	55	Rx5p	Receiver Non-Inverted Data Output
18	Rx1n	Receiver Inverted Data Output	56	Rx5n	Receiver Inverted Data Output
19	GND	Ground	57	GND	Ground
20	GND	Ground	58	GND	Ground
21	Rx2n	Receiver Inverted Data Output	59	Rx6n	Receiver Inverted Data Output
22	Rx2p	Receiver Non-Inverted Data Output	60	Rx6p	Receiver Non-Inverted Data Output
23	GND	Ground	61	GND	Grounds
24	Rx4n	Receiver Inverted Data Output	62	Rx8n	Receiver Inverted Data Output
25	Rx4p	Receiver Non-Inverted Data Output	63	Rx8p	Receiver Non-Inverted Data Output
26	GND	Ground	64	GND	Ground
27	ModPrsL	Module Present	65	NC
28	IntL	Interrupt	66	Reserved
29	VccTx	+3.3V Power Supply Transmitter	67	VccTx1	+3.3V Power Supply Transmitter
30	Vcc1	+3.3V Power Supply	68	Vcc2	+3.3V Power Supply
31	LPMode	Low Power Mode	69	Reserved
32	GND	Ground	70	GND	Ground
33	Tx3p	Transmitter Non-Inverted Data Input	71	Tx7p	Transmitter Non-Inverted Data Input
34	Tx3n	Transmitter Inverted Data Input	72	Tx7n	Transmitter Inverted Data Input
35	GND	Ground	73	GND	Ground
36	Tx1p	Transmitter Non-Inverted Data Input	74	Tx5p	Transmitter Non-Inverted Data Input
37	Tx1n	Transmitter Inverted Data Input	75	Tx5n	Transmitter Inverted Data Input
38	GND	Ground	76	GND	Ground

QSFP-DD Module Pad Layout

Control Signals

This head end of the MCP7H60 is QSFP-Double Density and QSFP28 and the ‘tails’ are QSFP28. This means that the control signals shown in the pad layout and the pin assignments have the following functions:

Name	Function	Description
ModPrsL	Output, asserted low	Pull-up by host when no cable is present. The cable is connecting the signal to ground. Hence, asserted when the cable is plugged in.
ModSelL	Input, asserted low	Asserted by host to activate the I2C (two-wire interface) to the EEPROM inside the cable.
ResetL	Input, asserted low	Must be de-asserted to enable the host system to read the EEPROM.
LPMode	Input, asserted high	Not connected in DAC cables.
IntL	Output, asserted low	Not used in DAC cables, internally pulled high.

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QSFP28 Pin Description

QSFP28 Module Pad Layout

QSFP-DD Pad Description

QSFP-DD Module Pad Layout

Control Signals