User's Manual

To place the HT750 into bootstrap mode, it must be reset while the BOOT-CNTRL (J30-
28) pin is grounded. This pin is grounded when the programming cable is connected and
the flash adaptor switch is turned on. Refer to Figure ?.
When the BOOT-CNTRL line is grounded, Q100 which controls U102 and U105, is
opened and 9.6V passes through U102-2 to the base of Q112. Q113 opens and
disconnects SW7.5V from 7.5V. At this point there is no supply voltage to the HT750.
Meanwhile, 9.6V is also applied to the base of Q112 thus charging up capacitor C182.
After approximately 1.5 seconds, C182 is charged to a voltage that saturates Q111,
causing Q112 to open and Q113 to turn On. SW7.5V is connected back to 7.5V again.
At this point the HT750 has been reset and is now in bootstrap mode.
To prevent mobile bus messages from corrupting the flash programming of the HT750,
the control signals to U102-3, U105-2 and U105-3 are applied with 9.6V to disconnect
the Bus+ (P102-5), Bus- (P102-14) and Busy (P102-23)lines from the mobile when the
BOOT-CNTRL line is grounded.
Program Sense:
The PROG_SENSE signal(J30-10) is monitored by the VRS to detect when the
programming cable is connected at connector P101. This line will be pulled to ground
when the programming cable is connected or will be 3.3VDC when the programming
cable is not connected.
The programming cable is used when adjusting the VRS using the Tuning Tool (refer to
section ?) or when updating the VRS firmware using the VRS750 Upgrade Tool (refer to
section ?).
Mode Configuration:
There are various operating modes of the VRS750. The mode is selected at power-up
based on the settings of dipswitch S1 pins 1, 2 and 3. Pin 4 is unused. The following
table shows the supported modes:
Operating Mode S1 Pin 1 S1 Pin 2 S1 Pin 3
Normal On On On
Test Mode Off Off Off
ATE Test Mode On Off Off
HT750 CPS Mode Off On On
Normal mode is the default and standard configuration for the VRS750. Test Mode and
ATE Test Modes are used by Motorola for testing purposes. HT750 CPS Mode is
available for when the user requires the transmit and receive frequencies to differ.
Operation during this mode is not advised and if required please contact your Motorola