Motorola MCS 2000 Service Instructions Manual page 116

8-6
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 via R0689/
R0690 network and switches the multiplexer to keyload mode via U0654 (Q1). This action overrides
the current sensor device.
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 via the
multiplexer to the µC A/D port where the analogue voltage is measured and decoded for all four
possible combinations of PTT/Monitor and the 4 Auxiliary levels.
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 (Q0660, Q0661 and U0656) 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 DVP WE (DVP 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 (DVP WE), pin 12 (KID) and pin 11 (Key/Fail).
December 6, 2004
Control Heads: Models II and III
68P81083C20-D