DS80PCI102: DS80PCI102 Receiver_Detect mechanism

Moving to high speed interface

The presence of a valid receiver termination impedance is detected by the output.  If a valid termination is present, the input termination on the DS80PCI102 is configured to be active or "on".  If no valid receiver termination is attached to the DS80PCI102 output, the input termination is in-active or "off".  

In this way the DS80PCI102 "mirrors" the termination impedance it detects on its output pins by setting the input terminations to match them.

Regards,

Lee 

If I understand correctly, the DS80PCI102 receiver termination stays high impedance until the same channel transmitter detects a valid receiver. Then my next two questions are:

1. How does DS80PCI102 determine a valid receiver being attached? Per PCIe spec the Receiver_Detect mechanism looks for an impedance change, instead of a simple 80-120 ohm termination. Does DS80PCI102 transmitter look for an impedance change or just static 80-120 ohm termination?

2. When does DS80PCI102 transmitter start "looking for" valid receiver termination with respect to the following edge of PRSNT#?

Hi XY,

1. The DS80PCI102 determines a valid receiver is attached by shifting the output common mode voltage on the p/n output signals simultaneously. If the voltage response indicates Hi-Z then no receiver is present.  If the voltage response indicates 50 Ohms to GND or VDD then a receiver is present.

The outputs will test for a receiver every 12ms. 

2. The outputs will begin looking for a valid receiver as soon as the device powers up and PRSNT# = L

Regards,

Lee

Lee,

For #2, would you quantify "as soon as" in timing unit?

Thanks.. XZ

XY,

From power-up with PRSNT# = L when power is applied, the first RXDET output pulse will be seen approximately 36mS after the power supply reaches the recommended voltage range.

If the power is already in a valid range and PRSNT# = H, the first RXDET output pulse will be seen approximately 12mS after the PRSNT# pin transitions from H -> L

Assuming our device detects a valid termination on the first two attempts, the input termination will be mirrored in an additional 12mS.

The time from power-up to mirrored input termination with PRSNT# = L at power-up = 48mS
The time from PRSNT# = H -> L to mirrored input termination with power already applied = 24mS

Regards,
Lee