AM7968-125JC datasheet(106/127 Pages) AMD

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TAXIchip Integrated Circuits Technical Manual

TAXI Technical Information Publication #89-08

Subject: TAXI Receiver Lock Time

Question:

In a fully operational system in which both the Transmitter and Receiver are powered

on, how long will it take for the Receiver to lock to new data after a quiet line?

Answer:

When data transmission stops and the link becomes quiet, the TAXI Receiver PLL will

drift to its natural resting frequency which by design, is less than 3% away from the

reference frequency applied at the X1 pin.

When data appears on the line, the Receiver PLL will achieve phase lock in a time

which is proportional to the incoming data edge density and PLL loop bandwidth.

Because this lock time is dependent on the data being transmitted, the time it takes for

the receiver to lock will depend on the specific system application. In Section 3.3, three

types of data are represented and their calculated lock times are shown. By dividing the

lock time for a specific data pattern by the X1 clock period, the number of bytes to lock

the PLL can be calculated.

Because time to lock is dependent on many variables, it is represented as a typical time.

If time to lock is critical to the specific application, we suggest you allow at least the

times shown.

Although there is no guaranteed specification for time to lock, a test is run (using a JK

pattern) as part of AMD outgoing tests to ensure that all devices can achieve lock within

a reasonable time. The test is performed by sending JKs for 640

µs, and then without

interruption, a full rate functional test is run. For the test to pass, the PLL must lock to

the JK pattern and then track the incoming data perfectly.

AM7968-125JC Datenblatt(PDF) 106 Page - Advanced Micro Devices