MSC711x Application Development System (MSC711xADS) Reference Manual, Rev. 1
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Freescale Semiconductor
MSC711xADS Interfaces
• Ground key detection.
• DTMF detection.
• Fax and modem tone (1100 Hz and 2100 Hz) detection.
• DC loop current limit.
• Ring generation.
• Subscriber line impedance matching.
• Metering signal generation.
• Line circuit test.
If the dual VoSLAC device is to accomplish these functions, it must receive input from the dual VoSLIC device,
which senses the following parameters and scales them appropriately for the dual VoSLAC device:
• VIN: A metallic AC voltage that is proportional to the upstream AC loop current.
• IMT: A current that is proportional to the DC + AC loop current.
• F: A logic low indicates a fault or ground key condition.
The dual VoSLAC device then outputs the following to the dual VoSLIC device:
• VDC: DC loop current limit threshold control voltage.
• VOUT: Downstream voice and low level metering signals or internal ringing or test signals.
The Dual VoSLAC device performs the codec and filter functions associated with the 4-wire section of the
subscriber line circuitry in a digital switch. These functions involve converting an analog voice signal into digital
PCM samples and converting digital PCM samples back into an analog signal. During conversion, digital filters are
used to band-limit the voice signals. The user-programmable filters set the receive and transmit gain, perform the
trans-hybrid balancing function, permit adjustment of the 2-wire termination impedance, and provide frequency
distortion adjustment (equalization) of the receive and transmit paths. An adaptive trans-hybrid balance filter is
included to allow the VoSLAC device to adjust to changing line conditions dynamically, minimizing objectionable
echo. All programmable digital filter coefficients can be calculated using WinSLAC software. The PCM codes can
be 16-bit linear two’s complement, 8-bit complement, A-law or µ -law, or 32 kbps or 24 kbps ADPCM.
5.12 E1/T1 Framer
The PMC PM4351-NI framer supports one network line and contains analog and digital function blocks configured
and controlled by the MSC711xADS host. The PMC PM4351-NI framer performs many functions and is well
suited to a wide range of networking applications. It handles all the required interfacing between analog E1/T1/J1
lines and the digital PCM system highway.