Cyclone V Device Handbook: Volume 2: Transceivers

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

1.2.1.2.1. Transmitter Buffer Features and Capabilities

Table 5.  Transmitter Buffer Features
Feature Capability
Programmable Differential Output Voltage (VOD) Up to 1200 mV of differential peak-to-peak output voltage
Programmable Pre-Emphasis Support first Updated the Post Tap Pre-emphasis setting
On-Chip Biasing for Common-Mode Voltage (TX VCM) 0.65 V
Differential OCT 85, 100, 120, and 150 Ω
Transmitter Output Tri-State Supports the electrical idle function at the transmitter as required by the PCIe Base Specification 2.0 for Gen1 and Gen2 signaling rates
Receiver Detect Supports the receiver detection function as required by the PCIe Base Specification 2.0 for Gen1 and Gen2 signaling rates
Figure 10. Example of the Pre-Emphasis Effect on Signal Transmission at the Transmitter OutputSignal transmission at the transmitter output with and without applying pre-emphasis post-tap for a 3.125 Gbps signal with an alternating data pattern of five 1s and five 0s.


You can AC-couple the transmitter to a receiver. In an AC-coupled link, the AC-coupling capacitor blocks the transmitter common-mode voltage. At the receiver end, the termination and biasing circuitry restores the common-mode voltage level that is required by the receiver.

Figure 11. AC-Coupled Link with a Cyclone V TransmitterThe PCIe spec requires that you enable transmitter OCT for receiver detect operation.