Cross timestamping for pci express precision time measurement

A method for precision time management (PTM) facilitating cross timestamping, the method comprising:

• sending a data packet that is associated with a transmit signal (Tx) to a host device, the Tx including a request transmission time, the Tx causing the host device to generate a timestamp at a second time T2;
• receiving a receiver signal (Rx) associated with the data packet from the host device, the Rx including a response transmission time, the Rx being sent from the host device at a third time T3;
• determining the request transmission time and the response transmission time;
• determining, based on the T2 and the request transmission time, a first time T1 that the data packet was sent to the host device, where T1 represents a rising edge of a clock signal of a PTM system;
• determining, based on the T3 and the response transmission time, a time T4 that the data packet was received from the host device, where T4 represents a falling edge of the clock signal of the PTM system;
• comparing the rising edge and the falling edge to a total propagation delay associated with a precision time protocol (PTP) to determine a clock phase between the PTP and the clock signal of the PTM system;
• and
• cross timestamping the clock signal of the PTM system with the PTP;
• wherein the T1, the T2, the T3, and the T4 are timestamped in nanoseconds.

A non-transitory computer-readable storage medium, the computer-readable storage medium storing instructions that when executed by a processor cause the processor to:

• send a data packet that is associated with a transmit signal (Tx) to a host device, the Tx including a request transmission time, the Tx causing the host device to generate a timestamp at a second time T2;
• receive a receiver signal (Rx) associated with the data packet from the host device, the Rx including a response transmission time, the Rx being sent from the host device at a third time T3;
• determine the request transmission time and the response transmission time;
• determine, based on the T2 and the request transmission time, a first time T1 that the data packet was sent to the host device, where T1 represents a rising edge of a clock signal of a precision time management (PTM) system;
• determine, based on the T3 and the response transmission time, a fourth time T4 that the data packet was received from the host device, where T4 represents a falling edge of the clock signal of the PTM system;
• compare the rising edge and the falling edge to a total propagation delay associated with a precision time protocol (PTP) to determine a clock phase between the PTP and the clock signal of the PTM system;
• and
• cross timestamp the clock signal of the PTM system with the PTP;
• wherein the T1, the T2, the T3, and the T4 are timestamped in nanoseconds.