Models Ii And Iii; Introduction; Power Supplies - Motorola MCS 2000 Service Instructions Manual

Control Heads: Models II and III
When the connected device is an SB9600 device, the current is greater than 2 mA and the
multiplexer is switched to SB9600 mode. Note that when an SB9600 device is self-powered, i.e. no
current consumption from the microphone connector, a dummy load must be connected to pin 1 to
ensure a minimum current of 2 mA and force the multiplexer into the SB9600 mode. A field
programmer is an example of such a device.
In the Secure keyload mode, an A/D input on the µC U0653 (PD6) monitors the Speaker-output dc
voltage.
If the output is short circuit to ground for more than 1 second, the µC senses this and switches to
keyload mode (via PC7 output).
Normal Mode
Typically a microphone with no microprocessor is connected to the microphone connector. Inputs in
this mode include PTT, Monitor and Auxiliary. In Normal mode these inputs are routed to the µC A/D
port where the analogue voltage is measured and decoded for all possible combinations of PTT,
Monitor and Auxiliary.
SB9600 Bus Mode
Typically a control microphone, intelligent handset or field programmer is connected to the
microphone connector. Inputs include Bus+, Bus- and Busy.
On selection of this mode Bus+ and Bus- are routed from the multiplexer via the bus comparator
circuit (Q0655, Q0656 and U0652) to the µC bus interface (RD1/TD0). Busy is routed to the radio via
the Busy line (pin 14).
Secure Mode
This is the secure keyload mode. The inputs in this mode include WE (Write Enable), KID (Key Insert
Data) and Key Fail. On selection of this mode these inputs are routed from the multiplexer to the
radio via pin 10 (WE), pin 12 (KID) and pin 11(Key Fail).

Models II and III

Introduction

The Control Head forms the interface between the radio and the user. It contains an LCD display, on/
off and volume switch, keypad and control keys. Control Head model II contains a rotary switch in
place of a full keypad.
The microprocessor controlled Control Head interfaces to the radio control logic board J0650 via an
18-pin connector on the back of the unit. An external microphone/speaker is connected to the
Control Head via the front mounted microphone connector P0651.

Power Supplies

Power supply A+ (pin 17) is routed directly from the radio through the 18-pin connector and is used
for LCD and keypad backlight LEDs and indicator LEDs.
Power supply B+ (pin 18) is routed from the radio battery via the radio on/off switch. It is routed to the
microphone connector current sensor device (Q0664) and provides Vcc via regulator U0650.
Option SW B+ (pin 1) is the power supply output to the connected accessory. The current is
monitored by the Control Head to operate the multiplexer. (Refer to Mode Select)
68P81083C20-D
8-3
December 6, 2004