Electrical Compliance

R

maximum allowed frequency, and the frequency may change on a cycle-by-cycle basis. Under certain conditions, the PCI core may also apply phase shifts to this clock.

For these reasons, the user application should not use this clock as an input to a DLL or PLL, nor should the user application use this clock in the design of interval timers (for example, DRAM refresh counters).

Electrical Compliance

The PCI interface targeting Virtex devices uses one of three Virtex I/O buffer types, depending on the signaling environment (this selection is made via the wrapper file).

Note: Virtex-E, Virtex-II, Virtex-II Pro, Virtex-4, Spartan-IIE, Spartan-3, and Spartan-3E devices are not 5.0 volt tolerant. Do not use these devices in a 5.0 volt signaling environment.

Wrapper files for the 5.0 volt signaling environment use the PCI33_5 I/O buffers available

on Virtex and Spartan-II devices. This requires VCCO to be set at 3.3 volts, and does not require a VREF supply. Observe the relevant specifications in the device data sheet. No

other restrictions apply.

Wrapper files for the 3.3 volt signaling environment use either the PCI33_3 or the PCI66_3 I/O buffers available on Virtex, Virtex-4, Virtex-E, Virtex-II, Virtex-II Pro, Spartan-II, Spartan-IIE, Spartan-3, and Spartan-3E devices. With the exception of Virtex-II Pro,

Virtex-4, Spartan-3, and Spartan-3E, these require VCCO to be set at 3.3 volts, and do not require a VREF supply. Observe the relevant specifications in the device data sheet.

For 3.3 volt signaling in Virtex-E, Virtex-II, Virtex-II Pro, Virtex-4, Spartan-IIE, Spartan-3, and Spartan-3E devices, no other restrictions apply. However, additional restrictions do apply for 3.3 volt signaling in Virtex and Spartan-II devices—for 3.3 volt signaling in Virtex and Spartan-II devices, the data sheets indicate that the VIL and VIH parameters for the

input buffers are a function of VCCINT, which is a 2.5 volt supply. In the PCI Local Bus Specification, the specifications for the 3.3 volt signaling environment state VIL and VIH as

a function of VCC. This may be considered the 3.3 volt system supply.

When the 2.5 volt and 3.3 volt supplies are at their opposite extremes, the 3.3 volt VIL or VIH specifications will be violated. The violation is only technical, and will not affect functionality. The VIL or VIH will not venture beyond the parameters stated in the PCI Local Bus Specification to affect noise margins significantly. For all supply combinations, VIL will always be within 35 mV of the specification, and VIH will be within 75 mV of the specification. They cannot both be out of specification simultaneously.

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PCI v3.0 specifications

Xilinx PCI Express (PCIe) v3.0 technology represents a significant leap in performance and efficiency for high-speed data transfer applications. As a critical interface standard for connecting peripheral devices to a host system, PCIe v3.0 introduces numerous enhancements that ensure faster data rates, increased bandwidth, and lower latency, meeting the rigorous demands of modern computing environments.

One of the standout features of PCIe v3.0 is its increased data transfer rate, which doubles the bandwidth compared to its predecessor, PCIe v2.0. This version supports a maximum theoretical bandwidth of 8 GT/s (gigatransfers per second) per lane, leading to an aggregate bandwidth of up to 32 GB/s with four lanes operating simultaneously, which is crucial for applications in data-intensive fields such as telecommunications, data centers, and high-performance computing.

Xilinx’s PCIe v3.0 solutions incorporate advanced error-handling mechanisms and improved power management. The technology employs a robust 128/130b encoding scheme that minimizes overhead while ensuring data integrity. Additionally, PCIe v3.0 supports native high-speed signaling, which not only reduces power consumption but also enhances signal quality, leading to greater reliability in data transmission.

The flexibility of Xilinx’s PCIe v3.0 implementation makes it ideal for various applications, including artificial intelligence, machine learning, and video processing, where rapid data throughput is paramount. Moreover, Xilinx provides extensive support through its Vivado Design Suite, enabling developers to easily integrate PCIe functionality into their designs while optimizing performance for specific applications through customizable settings.

Another key characteristic is the backward compatibility with earlier PCIe versions. This ensures that existing hardware can leverage new capabilities without necessitating a complete overhaul of the infrastructure, enhancing investment protection for users. The inclusion of additional features such as enhanced message signaling and the ability to support up to 64 thousand in-flight transactions further boosts the efficiency of data handling in a multi-threaded environment.

In summary, Xilinx PCI Express v3.0 technology is a powerful solution that combines high bandwidth, reduced latency, and enhanced reliability, making it an essential component for advanced computing architectures. Its robust features, coupled with Xilinx’s design tools and support, provide developers with the resources needed to push the boundaries of data transfer capabilities in a growing range of applications.
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