Motorola Gm328 Gm338 Gm398 Detailed 6804112j18 E Manual

Controller Circuits1-9
There are 8 analogue to digital converter ports (A/D) on U0101. They are labelled within the device 
block as PE0-PE7. These lines sense the voltage level ranging from 0 to 5V of the input line and 
convert that level to a number ranging from 0 to 255 which can be read by the software to take 
appropriate action.
For example U0101-67 is the battery voltage detect line. R0671 and R0672 form a resistor divider 
on INT SWB+. With 30K and 10K and a voltage range of 11V to 17V, that A/D...

1-10Controller Circuits
1.13 FLASH Electronically Erasable Programmable Memory(FLASH EEPROM)
The 512KByte FLASH EEPROM (U0121) contains the radio’s operating software. This software is 
common to all open architecture radios within a given model type. For example Trunking radios may 
have a different version of software in the FLASH EEPROM than a non Trunking radio. This is, as 
opposed to the codeplug information stored in EEPROM (U0111) which could be different from one 
user to another in the same...

Controller Board Audio and Signalling Circuits 1-11
2.0 Controller Board Audio and Signalling Circuits
2.1 General - Audio Signalling Filter IC with Compander (ASFIC CMP)
The ASFIC CMP (U0221) used in the controller has 4 functions;
1) RX/TX audio shaping, i.e. filtering, amplification, attenuation
2) RX/TX signalling, PL/DPL/HST/MDC/MPT
3) Squelch detection
4) Microprocessor clock signal generation (see Microprocessor Clock Synthesizer Description).
The ASFIC CMP is programmable through the SPI BUS...

1-12 Controller Board Audio and Signalling Circuits
2.2.1 Mic/Data Input Path
The radio supports 2 distinct microphone paths known as internal (from controlhead) and external 
mic (from accessory connector J0501-2) and an auxiliary path (FLAT TX AUDIO, from accessory 
connector J0501-5). The microphones used for the radio require a DC biasing voltage provided by a 
resistive network.
These two microphone audio input paths enter the ASFIC CMP at U0221-48 (external mic) and 
U0221-46 (internal mic)....

Controller Board Audio and Signalling Circuits 1-13
The ASFIC has an internal AGC that can control the gain in the mic audio path. The AGC can be 
disabled / enabled by the µP. Another feature that can be enabled or disabled in the ASFIC is the 
VOX. This circuit, along with the capacitor at U0221-7, provides a DC voltage that can allow the µP 
to detect microphone audio. The ASFIC can also be programmed to route the microphone audio to 
the speaker for public address operation.
2.2.2 PTT Sensing and TX...

1-14 Controller Board Audio and Signalling Circuits
2.3 Transmit Signalling Circuits
Refer to 1-4 for reference for the following sections.
Figure 1-4 Transmit Signalling Paths
From a hardware point of view, there are 3 types of signalling:
1) Sub-audible data (PL / DPL / Connect Tone) that gets summed with transmit voice or signalling,
2) DTMF data for telephone communication in trunked and conventional systems, and
3) Audible signalling including Select 5, MPT-1327, MDC, High speed Trunking.
NOTE: All...

Controller Board Audio and Signalling Circuits 1-15
This drives a tone generator inside U0221 which generates a staircase approximation to a PL sine 
wave or DPL data pattern. This internal waveform is then low-pass filtered and summed with voice 
or data. The resulting summed waveform then appears on U0221-40 (MOD IN), where it is sent to 
the RF board as previously described for transmit audio. A trunking connect tone would be 
generated in the same manner as a PL tone.
2.3.2 High Speed Data
High speed...

1-16 Controller Board Audio and Signalling Circuits
2.4 Receive Audio Circuits
Refer to 1-5 for reference for the following sections.
Figure 1-5 Receive Audio Paths
2.4.1 Squelch Detect
The radio’s RF circuits are constantly producing an output at the discriminator (IF IC). This signal 
(DISC AUDIO) is routed to the ASFIC CMP’s squelch detect circuitry input DISC (U0221-2). All of 
the squelch detect circuitry is contained within the ASFIC CMP. Therefore from a user’s point of 
view, DISC AUDIO enters...

Controller Board Audio and Signalling Circuits 1-17
SQ DET is used to determine all audio mute / unmute decisions except for Conventional Scan. In 
this case CH ACT is a pre-indicator as it occurs slightly faster than SQ DET.
2.4.2 Audio Processing and Digital Volume Control
The receiver audio signal enters the controller section from the IF IC on DISC AUDIO. The signal is 
DC coupled by R0228 and enters the ASFIC CMP via the DISC pin U0221-2.
Inside the ASFIC CMP, the signal goes through 2 paths in...

1-18 Controller Board Audio and Signalling Circuits
If the voltage is between 3.3 and 6.4V, the device will be active but has its input (U0273-1/9) off. This 
is a mute condition which is used to prevent an audio pop when the PA is enabled.
The SPK+ and SPK- outputs of the audio PA have a DC bias which varies proportionately with FLT 
A+ (U0271-7). FLT A+ of 11V yields a DC offset of 5V, and FLT A+ of 17V yields a DC offset of 8.5V. 
If either of these lines is shorted to ground, it is possible that the...