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Analogue front end for dsp/fpga/mcu based systems

CML Microcircuits' CMX7861 'FirmCODEC' is a full featured analogue front end for dsp/fpga/microcontroller based systems.

According to CML, the device is a combination of codec, embedded signal processing and auxiliary system support functions, allowing simple interfacing between analogue and digital systems that together improve overall system performance, reduce development time and overall system cost.

Modern day electronic systems, notably communication, control and monitoring are increasingly migrating to digital operations, an area dominated by dsp/fpga/microcontroller signal processing. However, the real world is essentially analogue, making analogue to digital and digital to analogue interfaces a crucial part of the overall design. FirmCODEC is designed to provide this solution.

The device is intended for use in a number of applications including radio systems performing the main data conversion and auxiliary operations for monitoring and control, operating in channel bandwidths up to 50kHz and interfacing rf devices to baseband dsp/fpga/microcontroller. Single ended and differential interface options are provided and I/Q based operation is supported.

Fully programmable on chip independent dual channel, digital channel filters can be utilised for signal conditioning purposes. An Intelligent four channel SAR a/d converter, four independent d/a converters and GPIO subsystems are said to perform valuable functions and minimise host interaction and resources. Two synthesised system clock generators develop clock signals for off chip use. The C-BUS/SPI master interface expands host C-BUS/SPI ports to control external devices.

Two general modes of operation are supported: codec mode and modem mode.

Codec mode is intended for applications where a general purpose codec is required. When in codec mode, the CMX7861 will provide d/a and a/d conversion, and a front end intelligent codec for the dsp/fpga/microcontroller.
Modem mode is suited to applications where the CMX7861 is used to transmit and receive modulated data. Modem mode provides a transmit signal interpolator which is designed to aid in the modulation process by converting mapped symbols to a filtered, modulated output. Receive channel filters are also provided.

The CMX7861 utilises CML's proprietary FirmASIC component technology that enables on chip subsystems to be configured by a Function Image data file, which is uploaded during device initialisation and defines the device's function and feature set. The Function Image can be loaded automatically from a host microcontroller over the C-BUS serial interface or from an external memory device. The device's functions and features can be enhanced by subsequent Function Image releases, facilitating in the field upgrades.

The CMX7861 operates from a 3.3V supply and includes selectable power saving modes. It is available in a 64VQFN package.

Author
Chris Shaw

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