Main Controller Board for NEXUS Base Devices

• Base Device and routing control and monitoring
• Control-computer communication via Ethernet, RS 232, RS 422, or USB
• Synchronisation and clock-generation control
• Sample rates of up to 96 KHz
• Stores the current system status independently of the control computer
• Wordclock I/O, internal clock generator
• Test tone and noise generator
• Metering-information gathering

• Loudness metering and spectrum analysis (option)
• Temperature monitoring

 data sheet (124 kb)

The XCPU board is the main controller of NEXUS Base Devices and is pri­marily designed for controlling the routing, including redundant lines. It also handles the communication with an external control com­put­er, sys­tem management, and controls and monitors all system com­po­nents including power-supply units and backplanes. The external con­trol computer providing the graphical user interface is connected via an RS 232/422 or USB port. The changeover to the USB port occurs au­to­mat­i­cal­ly.
The XCPU 09 now features an Ethernet port simplifying integration into existing computer networks.
The USB port can now be used in parallel with the RS 232/422 interface. (The previous XCPU versions only allowed for either the USB or RS 232/422 formats to be used at one time.) A total of three RS 232/422 ports are available: one onboard interface plus two extra ports on the optional XDEM expansion. You select the RS format (RS 232 or RS 422) using a quadruple jumper.
The XCPU 09 includes an exceptionally powerful processor providing sub­stan­tial­ly more power than its predecessors. Therefore, the board can now perform extra tasks which used to be handled by external per­iph­erals.
The XCPU 09 implements two critical new functions as optional modules: EBU-R 128 compliant loudness metering and spectrum analysis. (Refer to the specifications sheet for details.)

Synchronisation

The XCPU board supports internally generated or externally refer­enced standard sample rates (44.1, 48, 88.2, or 96 kHz; other rates can be implemented on request). Synchronisation and clock generation are achieved using a PLL with an extended time constant for a low-jitter sys­tem clock.

The system provides the following sync modes:

• Internal sync — The generated wordclock is output via a BNC port for use as studio master clock.
• Synchronisation to an external wordclock. The board features a dedicated port for this purpose.
• Synchronisation to any digital port or to a fibre-optic line.
• Video-burst sync. Requires an optional XSYNC interface board.

Multiple sync sources can be set up. In the event of a sync source failure these sources are automatically selected according to a user-programmed priority list.

Test Tone Generator

The XCPU comprises a precision digital test tone generator with ad­just­able rate and level. In addition, the generator can produce white and pink noise. The digital audio signals are produced by a DSP. A D/A con­vert­er incorporated on the board makes the signal available in an an­a­logue format.

Metering

The board provides a peak-metering function that uses a DSP to detect the data of all 256 time slots and transfers this to the connected PC for viewing purposes.

Memory

The XCPU-board firmware is stored in flash memory and can therefore be updated using a service program running on the PC.
All volatile data is stored to a battery-backed SRAM. This ensures the most recent Base Device and system statuses are restored after pow­er failure or shutdown. The SRAM is backed-up by a conventional user-­replaceable lithium battery. The system displays a message when the battery needs replacement.
The XCPU also provides a micro-SD slot for future expansion.

Board ID

All Base Devices on the NEXUS audio network feature unique IDs. The IDs are selected using encoder switches on the physical XCPU board.