vpx

VPX

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VPX bus is a new generation of high-speed serial bus . The basic specifications, mechanical structure and bus signals of the VPX bus are all defined in the ANSI/VITA46 series of technical specifications.

 

Chinese name

VPX

bus

VITA

source

2VME bus

Technology

high-speed serial bus technology

content

1. 1 Overview
2. 2 bus structure
3. 3 high-speed connectors
4. 4 Power and cooling

Overview

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The VPX bus is derived from the VME bus, and the VME bus was born 30 years ago. It combines the Motorola company's Versa bus electrical standard and the European card mechanical packaging standard. It is an open architecture and has been used in industrial control, signal processing and defense. widely used.

But the VME bus is a technology 30 years ago after all. With the continuous improvement of the industry's requirements for the transmission bandwidth of the bus technology, the VME bus gradually revealed its drawbacks. To this end, VITA has also launched VME64 , VME64x, VME320 and other upgraded versions. Unfortunately, the market response is not very satisfactory. It was not until the advent of the VPX bus that this situation was completely reversed.

bus structure

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The VPX bus adopts the high-speed serial bus technology to replace the parallel bus technology of the VME bus. The VPX bus introduces the latest serial bus technologies, such as RapidIO, PCI-Express and 10 Gigabit Ethernet , to support higher backplane bandwidth . The VPX core exchange can provide 32 pairs of differential pairs, each pair of differential pairs can theoretically provide 10Gbps data exchange capability, and a VPX module can theoretically provide a maximum data exchange capability of 8GByte/s.

The VPX bus also adopts a switched structure to replace the master control structure of the VME. The switching structure makes the overall performance of the system not limited by the main control board, which improves the overall performance of the system. At the same time, under the switching structure, the processor can send data at any time without waiting for the bus to initiate transmission, which is especially suitable for multi- processor systems .

high-speed connector

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MultiGig RT2 Connector

One of the most important differences between the VME bus and the VPX is that the VPX bus uses a new generation of 7-row MultiGig RT2 connectors developed by Tyco. The MultiGig RT2 connector has excellent performance, not only the characteristic impedance is controllable, the insertion loss is low, but the crosstalk is still less than 3% when the transmission rate is up to 6.25Gbps. MultiGig RT2 connectors have tight and robust connections and can be used in harsh environments such as military and aerospace.

The VPX standard still uses the Oka 3U and 6U sizes in structure. One 8-column, 7-row RT2 connector P0 and six 16-column, 7-row RT2 connectors P1~P6 are defined on the 6U VPX board . Among them, P0 is a public connector, which provides maintenance management bus, test bus and power supply signal; P1 provides 32 pairs of differential pair signals and 8 single-ended signals; P1~P6 are user-defined, which can be defined as differential signals, It can also be defined as a single-ended signal. The 3U VPX board has only three connectors P0 to P2 in the 6U VPX board.

Power and Cooling

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The VPX bus improves the power supply capability. 5V can provide up to 115W of power, 12V can provide 384W, and 48V can provide 768W. In a slot of the VME bus, using a 5V power supply can only provide a maximum power of 90W, while the VPX bus can only provide 115W of power with a 5V power supply, and 12V and 48V power supplies can provide 384W and 768W of power. Such a high-power power supply enables the VPX daughter card to integrate more modules, and also makes the heat dissipation problem of the VPX bus architecture more serious. Therefore, the VPX bus provides three heat dissipation methods: air heat dissipation, metal conduction heat dissipation and liquid heat dissipation, which solves the heat dissipation problem of VPX very well.

In the following time, the VITA organization has made some upgrades to the VPX standard. There are two more important ones: one is VITA48, namely VPX-REDI, which mainly defines new definitions of heat dissipation and structural reinforcement to meet the needs of military and the harsh application environment in the aerospace field; the second is VITA65, namely OpenVPX, which mainly solves the problem that different manufacturers have different and incompatible definitions of P2 to P6. It redefines the system compatibility framework based on the VPX specification, which is a system-level standard. VPX bus has also become the bus .