Motorola ASTRO XTS 5000 Detailed Service Manual page 71

3-32
The USB transmitter is enabled when the RS232_USB* and USB_TXENAB signals are both driven
low by the dual-core processor. The single-ended data is output from the dual-core processor on the
UTXD1_USB_VPO pin and goes to USB1_DAT_TXD on U501. The data is driven out differentially
on the USB1_DP and USB1_DM pins, which go to the side connector. The dual-core processor
sends the single-ended zero signal from pin USB_VMO to the USB1_SE0 pin on U501.
When a USB cable is attached, pin CTS_CABLE_DET_5V is driven low and goes through level
translation in U501 and the output of CABLE_DET_3V is pulsed low and sent to the dual-core
processor. This line controls the USB and RS232 modes so that the data that is on those lines are
routed to the USB transceiver when a cable is detected. If a USB cable is not detected,
CABLE_DET_3V is high, the transceiver is put in suspend mode and the DP and DM pins can now
handle 5V tolerance for RS232 mode.
3.2.4.2.3 One-Wire Support
New options and accessories that attach to the side connector are identified by the dual-core
processor using the One-Wire protocol. The One-Wire pin on the side connector serves as the One-
Wire data pin. This signal is connected to the ONE_WIRE_OPT pin. This pin is connected to the
dual-core processor One-wire bus ONE_WIRE_UP through the Mako IC, U501, internal isolation
switch controlled by the SPI commands sent from the dual-core processor. 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, designator R245, of the side connector. When this occurs, the
digital-support IC pin KVL_USB_DET_X is asserted and the dual-core processor detects the
change. The dual-core processor then sends a command through the SPI lines to the U501 Mako IC
to connect the side connector One-Wire line to the dual-core processor One-Wire bus. In the case of
the USB cable, the dual-core processor reads the One-Wire data from the cable and, upon
determining that a USB cable is attached, programs the digital-support IC for USB mode.
3.2.4.2.4 Watchdog Timer
In kit NNTN5567A, the watchdog timer is a 125ms counter that is integrated into the MAKO IC U501
and used during the power down sequence. The MAKO IC will begin the power down sequence
when a low-to-high transition occurs on MECH_SW pin (MAKO pin E4). Once this transition occurs,
the MAKO IC begins the watchdog timer. Upon expiration, RESETX (MAKO pin C5) is asserted and
all of the MAKO regulators are shutdown. The dual-core processor can refresh the watchdog timer
so that the software has enough time to complete its tasks before the power is taken away.
3.2.4.2.5 32 kHz Oscillator and CMOS Output
There is an internal 32kHz oscillator circuitry to the MAKO IC U501 that is based off of a 32.768 kHz
crystal Y501 and additional load capacitors C501 and C502. The output of the 32 kHz oscillator is a
logic_vdd voltage (approximately 2.9 volts peak-to-peak), 32kHz +/- 20% square wave on pin
GATED_32K_CLK. This 32 kHz signal is routed through an analog switch U512 and sent to the dual-
core processor CKIL pin. This signal is only used to boot up the dual-core processor.
After the dual-core processor boots up, the select input (R599) of the analog switch is asserted high
allowing for the processor to receive an accurate 32.768 kHz, 2.9 V peak-to-peak square wave. This
signal is generated by tapping the output of the 32.768 crystal and buffering the signal with the
following components: U513, R545, R546, C543, C592, R542, and R541. The 32.768 kHz clock
signal allows for the completion of real-time applications.
3.2.4.3 ESD Protection Circuitry
See Figure 8-63, "NTN9564B VOCON Universal Connector Circuit," on page 8-97
details of the following discussion.
November 16, 2006
Theory of Operation
: VOCON Board
for schematic
6881094C31-E