Table of Contents
Advertisement
3-68
3.14.4.1 Power Turn-On
When SW_B+ is active at turn-on time, the voltage turns on Q0501, Q0504, and Q0505, which then
turns on SW_A+ via the power FET Q0503. SW_A+ then supplies all radio power (9.3-V regulators
and controller regulators). SW_A+ is derived the same way SW_B+ is at the control head.
SW_B+ is also sent to the comparator circuit, U0604, which allows the processor to monitor its level
via SW_B+_Sense (active high). When SW_B+ is sensed "on" by the processor, it asserts high an
output line, Soft_Turn_Off, to the wired-OR turn-on circuit at Q0502. This active-high processor
output is required for performing a soft power-down.
3.14.4.2 Power Turn-Off
At turn-off, SW_B+ becomes inactive at the control heads. As this voltage falls below 8.5 V, the
U0604 comparator circuit drives SW_B+_Sense low, telling the processor to power down the radio.
The processor eventually de-asserts low the SOFT_TURN_OFF signal after keeping the wired-OR
turn-on circuit, and thus SW_A+ and all radio power, on long enough to perform a soft power-down,
which includes deaffiliating on a trunked system, saving radio status parameters, etc. Once the
SW_B+ and SOFT_TURN_ON lines are both low, Q0502 and Q0504 turn off, which provides a low
at power FET Q0503. This turns off SW_A+, which removes all radio power.
3.14.4.3 Emergency Power-Up/-Down Sequence
The emergency input is provided to enable the radio transceiver to be activated, regardless of the
state of the control head's On/Off switch. The emergency input is activated by opening the normally
grounded footswitch connected to J0402, pin 28, of the controller. This input is routed to Q0501 and
to the same wired or turn-on circuit and SW_A+ FET.
Under normal configurations, the output of Q0501 goes low to trigger pin 2 of a monostable vibrator
U0506 causing the output pin 3 to go high. This enables the regulators through D0501 and Q0502. It
also enables the EMERG_SENSE line to the MCU through U0508-1. The monostable vibrator is a
timeout timer that holds the regulators on for 300 ms. This delay is required to allow the MCU to
initiate its start-up vectors and poll the EMEG_SENSE line J17 of U0001. The MCU takes control of
the regulators through D0501 and Q0502 by holding SOFT_TURN_OFF high.
The emergency active state depends on the emergency polarity into the timer. Normally with Q0501
present, emergency is active with the footswitch open. Removing Q0501 and adding R0527 causes
the emergency to go active with the switch closed.
3.14.5 MCU and DSP System Clocks
The MCU within the Patriot IC (U100) needs two clocks for proper operation. A 16.8 MHz sine-wave
reference is provided at the CKIH (A6) pin of the Patriot IC. The source of this clock is a 16.8 MHz
oscillator and its associated filtering circuitry. This clock is also provided to the Urchin IC (U0901).
The MCU has the capability of running at higher clock rates, which are programmable and based on
this 16.8 MHz reference. The DSP within the Patriot IC also uses the 16.8 MHz provided at the CKIH
(A6) pin as a reference.
The Patriot IC also requires a 32 kHz square-wave clock, provided at the CKIL (J7) pin. This clock is
generated by a 32 kHz crystal (Y0100), with supporting circuitry for oscillation. This clock is utilized
only for the Patriot IC, and is used for reset capability and other Patriot IC functions.
Four additional clocks are also supplied to the daughtercard: a 20 kHz RX frame-sync clock, a
48 kHz TX frame-sync clock, a 1.2 MHz RX data clock, and a 2.4 MHz TX data clock. The
microprocessor also generates the digital audio bus clocks: a 512 kHz data clock and an 8 kHz
frame-sync clock.
June 15, 2005
Theory of Operation: Controller Section
6815854H01-A
Advertisement
Table of Contents
Troubleshooting
