Radio Audio System - Motorola MTM700 Detailed Service Manual

THEORY OF OPERATION (400 MHz)
U0102-1 and U0102-2 perform buffering and level shifting from 3 volts to 5 volts level. The RedCap2
uses its UARTB for the SBEP serial interface.
RS232 and SB9600 Serial Interfaces
The configuration of the RS232 and SB9600 serial interfaces depends on the radio setup. If no
expansion head is connected to the radio, RedCap2 module UARTA provides either a 4-wire RS232
or an SB9600 interface on the 20 pin accessory connector J0400. If at power up pin BUSY_OUT on
the accessory connector J0400 is connected to pin BUSY_IN, the RedCap2 assumes that SB9600
equipment is connected and configures UARTA for the SB9600 interface. If both pins are not con-
nected to each other at power up, the UARTA will be configured for RS232 interface. The interface
comprises lines RS232_TX, RS232_RX, RS232_CTS, RS232_RTS. These lines are not buffered
and at 0 or 3 volts level.
An optional RS232 interface board can be fitted in the accessory connector J0400 when no expan-
sion head is connected. This board provides a 4-wire RS232 interface with standard RS232 levels
available on the 7 pin connector P0701. The RedCap2 uses its QSPIB module for this interface.
If an expansion head is connected to the radio, the serial interfaces on the 20 pin accessory connec-
tor J0400 can not be used. The UARTA is configured for an 8-wire RS232 interface, which is availa-
ble on the 9 pin connector of the expansion head. This interface has standard RS232 levels and can
be connected to an external data terminal. In addition, the RedCap2 configures its QSPIB module to
provide either a 4-wire RS232 or SB9600 interface with 5 volts level on the 25 pin expansion head
connector. If line MUX_CTRL_1 is at 0 volt, the interface is switched to RS232 mode. If line
MUX_CTRL_1 is at 3 volts, the interface is switched to SB9600 mode. The interface comprises lines
BUSY_IN, BUSY_OUT, RESET_OUT, and the QSPIB lines SPIB_MOSI, SPIB_MISO, SPIB_CLK,
SPIB_CS1_UART and is available on the 40 pin front connector J0500 with signals at 3 volts high
level. The RedCap2 uses the SB9600 interface to communicate with the motorcycle control head. If
no motorcycle control head is connected, the interface can be used to control the radio via the
SB9600 protocol with an external control terminal.

Radio Audio System

External Mic
Internal Mic
Tx Audio
Handset
Audio
Speaker +
Speaker -
SP Audio
RX Audio
MTM700 Mobile Radio / Detailed Service Manual
U0201
MUX
U0206-2
MUX
U0205
Audio PA
Figure 8 Audio Block Diagram
U0206-4
U0203
U0202
U0204
U0206-1
4.1 - 21
FL0200
A/D
DSP
A/D