Backlight Driver And Led's; Voice Storage; 900 Mhz Transmitter; Figure 7-10. Transmitter Block Diagram - Motorola HT Series Service Manual

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7.9.4.5 BackLight Driver and LED's

The logic level signal from the radio microcontroller is translated via Q611 and applied to Q610 which
uses Switched Battery Voltage (SWB+) to operate the keypad backlight LED's.

7.9.4.6 Voice Storage

The Voice Storage (VS) 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 PTCB hosts the Voice Storage circuitry. Voice Storage IC U611 provides all the required
functionality and is powered from the regulated 5 volts. The mP controls U611 via SPI bus lines CLK
(U611-8), DATA (U611-10) and MISO (U611-11). To transfer data, the mP first selects the U611 via
line VS CS and U611 pin 9. Then the mP sends data through line DATA and receives data through
line MISO. Pin 2 (RAC) of U611 indicates the end of a message row by a low state for 12.5 ms and
connects to mP pin 65. A low at pin 5 (INT), which is connected to mP pin 55, indicates that the Voice
Storage IC requires service from the mP.
Audio, either from the radio's receiver or from one of the microphone inputs, emerges from the
ASFIC CMP (U404) at pin 43, through switch U608-1 that is selected by the mP via ASFIC CMP pin
5 (DACR) and then enters the voice storage IC U611 at pin 25. During playback, the stored audio
emerges from U611 at pin 20. To transmit the audio signal, it is fed through resistive divider R657 /
R658, through switch U608-3 and through line EXT MIC. When this path is selected, 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 U611 pin 20 is buffered by op-amp U605-1, through
switch U608-2 and fed via 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. Switches U608-2 and U608-3 are controlled by the mP via ASFIC CMP
pin 6 (DACG) and feed the stored audio only to the ASFIC CMP port UIO when it is programmed as
input.

7.10 900 MHz Transmitter

From VCO
Low Band, 800 MHz, PassPort & 900 MHz Theory of Operation: 900 MHz Transmitter
PCIC
Vcontrol
Power Amplifier (PA)
PA
Driver

Figure 7-10. Transmitter Block Diagram

Vcontrol
Antenna Switch/
PA Final
Harmonic Filter
Stage
Antenna
Jack