| Transmitter and Receiver Timings |
| UI (Gen1) | Unit Interval – PCI Express | 399.88 | 400.12 | ps | | 5 |
| UI (Gen 2) | Unit Interval – PCI Express | 199.9 | 200.1 | ps | | 5 |
| UI (GEN3) | Unit Interval – PCI Express | 124.96 | 125.03 | ps | | |
| TTX-EYE (Gen 1/Gen 2) | Minimum Transmission Eye Width | 0.75 | — | UI | Figure: PCI Express* Transmitter Eye | 1,2 |
| TTX-EYE-MEDIAN-to-MAX-JITTER (Gen 1) | Maximum time between the jitter median and maximum deviation from the median | 0.125 | — | UI | | 1,2 |
| TRX-EYE (Gen 1) | Minimum Receiver Eye Width | 0.4 | — | UI | Figure: PCI Express* Receiver Eye | 3,4 |
| TRX-EYE (Gen 2) | Minimum Receiver Eye Width | 0.6 | — | UI | | 3,4 |
- Specified at the measurement point into a timing and voltage compliance test load and measured over any 250 consecutive TX UIs. (also refer to the Transmitter compliance eye diagram)
- A TTX-EYE = 0.70 UI provides for a total sum of deterministic and random jitter budget of TTXJITTER-MAX = 0.30 UI for the Transmitter collected over any 250 consecutive TX UIs. The TTXEYE-MEDIAN-to-MAX-JITTER specification ensures a jitter distribution in which the median and the maximum deviation from the median is less than half of the total TX jitter budget collected over any 250 consecutive TX UIs. It should be noted that the median is not the same as the mean. The jitter median describes the point in time where the number of jitter points on either side is approximately equal as opposed to the averaged time value.
- Specified at the measurement point and measured over any 250 consecutive UIs. The test load documented in the PCI Express* specification 2.0 should be used as the RX device when taking measurements (also refer to the Receiver compliance eye diagram). If the clocks to the RX and TX are not derived from the same reference clock, the TX UI recovered from 3500 consecutive UI must be used as a reference for the eye diagram.
- A TRX-EYE = 0.40 UI provides for a total sum of 0.60 UI deterministic and random jitter budget for the Transmitter and interconnect collected any 250 consecutive UIs. The TRX-EYE-MEDIAN-to--MAX-JITTER specification ensures a jitter distribution in which the median and the maximum deviation from the median is less than half of the total 0.6 UI jitter budget collected over any 250 consecutive TX UIs. It should be noted that the median is not the same as the mean. The jitter median describes the point in time where the number of jitter points on either side is approximately equal as opposed to the averaged time value. If the clocks to the RX and TX are not derived from the same reference clock, the TX UI recovered from 3500 consecutive UI must be used as the reference for the eye diagram.
- Nominal Unit Interval is 400 ps for 2.5 GT/s and 200 ps for 5 GT/s.
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