Motorola ASTRO XTS 5000 Detailed Service Manual page 69

3-30
When a USB cable is detected, the USB_DIS pin (Q302 pin 2) goes high. This controls the isolation
switch Q301 so that the data that is on those lines are routed to the USB transceiver. If a USB cable
is not detected, the USB_DIS pin is low and the USB transceiver on the Flipper IC is isolated from
the side connector. This isolation is done primarily because the RS232 data lines are 5 V lines, so
the switch protects the transceiver since it operates at a lower voltage, and the USB data lines to the
side connector also act as the RS232 lines.
On the NNTN4717 VOCON board, the USB transceiver on the Flipper IC is not used. Instead, a
discrete USB transceiver U310 is used. This transceiver is provided with 5 V and 2.9 V. The 5 V
powers an internal 3.3 V voltage regulator on the transceiver, which is used as the voltage for the
USB data pins D+ an D- as well as the VPU pin. The 2.9 V is used by the remaining pins as they
interface to the dual-core processor U401.
3.2.4.1.3 One-Wire Support
New options and accessories that attach to the side connector are identified by the Patriot IC using
the One-Wire protocol. The Option Select 2 pin on the side connector also serves as the One-Wire
data pin (R218). This signal is connected to the ONE_WIRE_OPT pin. This pin is connected to the
Patriot IC One-Wire bus ONE_WIRE_UP through an internal isolation switch controlled by a Patriot
IC GPIO line to the Flipper IC ONE_WIRE_EN_X pin. This isolation is needed to prevent possible
contention on the One-Wire bus when a smart battery is attached to the radio.
These new accessories are to ground pin 10, CTS (TP208), of the side connector. When this occurs,
the Flipper IC pin KVL_USB_DET_X is asserted and the Patriot IC detects the change. The Patriot
IC then asserts the ONE_WIRE_EN_X pin on the Flipper IC to connect the side connector One-Wire
line to the Patriot IC One-Wire bus. In the case of the USB cable, the Patriot IC reads the One-Wire
data from the cable and, upon determining that a USB cable is attached, programs the Flipper IC for
USB mode.
3.2.4.1.4 Watchdog Timer
The Flipper IC monitors the position of the radio's On/Off switch on the BP_SEN_X pin, and that
signal is located on Q508 pin 3. If the voltage on pin 3 is ground, then the radio is turned on. If the
voltage on pin 3 is 3 volts, then the radio is off. When the radio is turned off, a counter inside the
Flipper IC begins incrementing. That counter can be refreshed by the Patriot IC through the SPI bus.
This is done so that the software has enough time to complete its tasks before the power is taken
away from the Patriot IC. If the counter is not refreshed by the time the count is complete, the Flipper
IC pin WD_OUT goes low, which shuts down the GCAP II voltage regulators. During normal radio
operation, WD_OUT should be high (V2 regulated voltage).
3.2.4.1.5 32 kHz Oscillator and CMOS output
The 32 kHz oscillator circuitry uses a separate voltage supply pin (VDD3_XTL) than the other 3-V
portions of the Flipper IC. This 32 kHz clock is used by the GCAP II RTC module to keep track of
time. The VDD3_XTS pin is supplied with the backup lithium (Li) rechargeable battery voltage
LI_CELL. The oscillator circuitry is internal to the Flipper IC, and the 32.768 kHz crystal Y301 and
additional load capacitors C308 and C309 are located next to the IC.
The output of the 32 kHz oscillator is an LI_CELL voltage (approximately 3 volts peak-to-peak),
32.768 kHz square wave on pin REF32_OUT. This clock goes to two destinations: the Patriot IC
CKIL pin (32 kHz test point) as a square wave and the GCAP II IC XTAL1 pin (C306) as a sine wave.
Components C306 and C313 are used to filter the square wave into a sine wave before the signal
goes to the GCAP II IC.
November 16, 2006
Theory of Operation
: VOCON Board
6881094C31-E