DisplayPort’s Multi-Monitor Feature Saves Power and Money

DisplayPort’s killer feature may be its ability to support multi-display monitors from a single digital output port and provide full display performance with zero latency, while consuming less power and costing less than other multi-monitor solutions.

By Ji Park and Henry Zeng, IDT

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Video/Imaging DesignWire
(11/13/2009 4:00:37 PM)

DisplayPort (DP) has come a long way from struggling to establish itself as the next external and internal video interface to become the de-facto next-generation PC interconnect, and a viable industry standard interconnect video interface. Given all of the options available today – VGA, DVI, HDMI; RGB, LVDS, mLVDS, RSDS, etc. – many in the industry wondered why another interface was necessary. With the combined promotion efforts of VESA members, which include system OEMs, chipset vendors and equipment vendors, DisplayPort has emerged as the next-generation video interface with full industry backing and alignment.

As we look to the future, the legacy analog interface and DVI interface will be phased out. This opens the door for DisplayPort, with its flexibility and next-generation features – such as multi-monitor support, to secure its place in the mainstream marketplace.

What is DisplayPort?
DisplayPort is a full digital video interface that is aimed at replacing LVDS as the internal interface of choice and replacing DVI/VGA as external interfaces. It uses a micro-packet-based architecture with an embedded clock vs. the traditional sequential data stream with separate clock and data, which is commonly seen in LVDS, DVI and VGA interfaces. In addition to the main video data, the micro-packets can also carry secondary digital audio data and enable unique features, such as multi-display and multi-monitor support. DisplayPort’s main data channels can be configured into 1, 2 or 4 high-speed SerDes lanes, with each lane providing 2.7 gbps or 1.62 gbps. The total bandwidth of up to 10.8 gbps is allowed within the current standard. Depending on the resolution size you want to support, the number of lanes can be minimized. With next-generation DisplayPort 1.2 looming, that bandwidth will be essentially doubled. This all happens while keeping a consistency of connector, cable and full backward compatibility and without fragmenting of existing or future DisplayPort standards.

The DisplayPort interface also includes a Hot Plug Detect (HPD) signal that is used to establish the link as well as to identify when a monitor is plugged into a PC. The HPD signals the source to establish a link through a process called link training. During this process, the source and receiver will also establish whether all of the four lanes are required.

Figure 1. DisplayPort Using the Auxiliary Channel and Hot Plug Detect (Source: VESA)

Unique to DisplayPort is the Auxiliary (AUX) channel, which is a slow speed “side channel” communication channel for link management, status, configuration and control by the source. The AUX channel provides 1 Mbps of data with next-generation features to encapsulate the USB 2.0 standard and enable bi-directional video and audio communication.

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