Cyclone V Device Handbook: Volume 2: Transceivers

ID 683586
Date 10/24/2018
Public
Document Table of Contents

1.2.3.1. Channel PLL Architecture

In LTR mode, the channel PLL tracks the input reference clock. The PFD compares the phase and frequency of the voltage controlled oscillator (VCO) output and the input reference clock. The resulting PFD output controls the VCO output frequency to half the data rate with the appropriate counter (M or L) value given an input reference clock frequency. The lock detect determines whether the PLL has achieved lock to the phase and frequency of the input reference clock.

In LTD mode, the channel PLL tracks the incoming serial data. The phase detector compares the phase of the VCO output and the incoming serial data. The resulting phase detector output controls the VCO output to continuously match the phase of the incoming serial data.

The channel PLL supports operation in either LTR or LTD mode.

Note: Use the LTR/LTD controller only when the channel PLL is configured as a CDR PLL.
Table 9.  Channel PLL Counters The Quartus® II software automatically selects the appropriate counter values for each transceiver configuration.
Counter Description Values
N Pre-scale counter to divide the input reference clock frequency to the PFD by the N factor 1, 2, 4, 8
M Feedback loop counter to multiply the VCO frequency above the input reference frequency to the PFD by the M factor 1, 4, 5, 8, 10, 12, 16, 20, 25
L (PFD) VCO post-scale counter to divide the VCO output frequency by the L factor in the LTR loop 1, 2, 4, 8
L (PD) VCO post-scale counter to divide the VCO output frequency by the L factor in the LTD loop 1, 2, 4, 8