MX812

The MX812 is a half-duplex VSR Codec, which when connected to an audio processing microcircuit (such as the MX816, 826 or 836), provides the storage and recovery of speechband audio in attached Dynamic RAM. The addition of this device will enhance the communications system by providing cellular radios with Answering Functions, "Message-Notepad" and general announcement cababilities.

The MX812 will enable:

• Storage of a speech message for transmission (replay) at a later time.

• Storage of a received speech message when the operator is not attending.

• The storage and subsequent replay of speech.

 All VSR operating functions are controlled by a simple serial mProcessor interface which may operate from the radio's own mProcessor/Controller.

Input audio from the "Store" output of the audio processor is digitized by delta modulation and stored via the DRAM controller, in attached memory. Audio for replay is recovered from the assigned memory locations and after demodulation made available for supply to the "Play" input of the audio processor. For use with other audio systems, the input/ output audio can be connected to relevant points in circuit.

The MX812 has no on-chip input or output audio filtering; this capability must therefore be provided by the host system. Sampling rates and memory capacity are selectable to 32kb/s or 63kb/s and 1 x 4Mbit or 2 x 1Mbit respectively, which when used in conjunction allow control of audio-quality and storage-time. This low-power CMOS device is available 28-pin plastic SOIC and 28-pin Cerdip packages.