Voice Storage (Optional) - Motorola GM328 Service Manual

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The output of the generator is summed into the audio chain just after the RX audio de-emphasis
block. Inside U0221 the tone is amplified and filtered, then passed through the 8-bit digital volume
attenuator, which is typically loaded with a special value for alert tone audio. The tone exits at
U0221-41 and is routed to the audio PA like receive audio
2.6

Voice Storage (optional)

The Voice Storage (VS) option can be used to store audio signals coming from the receiver or from
the microphone. Any stored audio signal can be played back over the radio's speaker or sent out via
the radio's transmitter.
The Voice Storage option can by placed on the controller section or on an additional option board
which resides on option board connector J0551. Voice Storage IC U0301 provides all required
functionality and is powered from 3.3 volts regulator U0351 which,is powered from the regulated 5
volts. Dual shottky diode D0301 reduces the supply voltage for U0301 to 3 volts. The
microprocessor controls U0301 via SPI bus lines CLK (U0301-8), DATA (U0301-10) and MISO
(U0301-11). To transfer data, the µP first selects the U0301 via address decoder U0141, line VS CS
and U0301 pin 9. Then the µP sends data through line DATA and receives data through line MISO.
Pin 2 (RAC) of U0301 indicates the end of a message row by a low state for 12.5 ms and connects
to µP pin 52. A low at pin 5 (INT), which is connected to µP pin 55 indicates that the Voice Storage
IC requires service from the µP.
Audio, either from the radio's receiver or from one of the microphone inputs, emerges the ASFIC
CMP (U0221) at pin 39, is buffered by op-amp U0341-1 and enters the Voice Storage IC U0301 at
pin 25. During playback, the stored audio emerges U0301 at pin 20. To transmit the audio signal it is
fed through resistive divider R0344 / R0345 and line VS MIC to input selector IC U0251. When this
path is selected by the µP via ASFIC CMP port GCB 4, the audio signal enters the ASFIC CMP at
pin 48 and is processed like normal transmit audio. To play the stored audio over the radio's
speaker, the audio from U0301 pin 20 is buffered by op-amp U0341-2 and fed via switch U0342 and
line FLAT RX SND to ASFIC CMP pin 10 (UIO). In this case, this ASFIC CMP pin is programmed as
input and feeds the audio signal through the normal receiver audio path to the speaker or handset.
Switch U0342 is controlled by the µP via ASFIC CMP port GCB 4 and feeds the stored audio only to
the ASFIC CMP port UIO when it is programmed as input.
Controller Board Audio and Signalling Circuits