Visible to Intel only — GUID: sam1403482118071
Ixiasoft
Visible to Intel only — GUID: sam1403482118071
Ixiasoft
2.2.1. Programmable Pre-Emphasis
The VOD setting and the output impedance of the driver set the output current limit of a high-speed transmission signal. At a high frequency, the slew rate may not be fast enough to reach the full VOD level before the next edge, producing pattern-dependent jitter. With pre-emphasis, the output current is boosted momentarily during switching to increase the output slew rate.
Pre-emphasis increases the amplitude of the high-frequency component of the output signal, and thus helps to compensate for the frequency-dependent attenuation along the transmission line. The overshoot introduced by the extra current happens only during a change of state switching to increase the output slew rate and does not ring, unlike the overshoot caused by signal reflection. The amount of pre-emphasis required depends on the attenuation of the high-frequency component along the transmission line.
Field | Assignment |
---|---|
To | tx_out |
Assignment name | Programmable Pre-emphasis |
Allowed values | 0 (disabled), 1 (enabled). Default is 1. |