Motorola ASTRO XTSTM 4000, Detailed Service Manual

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May 28, 2008 6871620L01-C
3-24 Theory of Operation: VOCON Section
The keypad lines are read through a row and column matrix made up of 7 row lines (UC_KP_ROW0
to UC_KP_ROW6) and 3 column lines (UC_KP_COLUMN0 to UC_KP_COLUMN2). A separate line
connects the ON/OFF button on the keypad to the ON/OFF Circuitry on the VOCON section
(UC_KP_ONOFF)
Keypad backlighting is supplied by the 5V Misc Regulator (U1101) and the backlight is controlled by
the Patriot IC GPIO KP_BLEN.
3.2.4.6 Buttons and Controls
The XTS4000 radio has the following buttons and controls:
• PTT button (PTT)
• Clear/ Secure mode button (P1)
• Emergency button (P2)
• Programmable button (P3)
• Volume Controls (VOL)
The P1, P2 and P3 buttons are connected to a resistor divider network, biased between V2 and
GROUND. The network, made up of R9913, R9914 and R9915 provides a DC voltage level,
controlled by whichever button is pressed, to pin 3 of buffer U1305. The output of buffer U1305 goes
to the MAKO ATOD_2 pin. The Patriot IC reads the MAKO A/D value through the SPI bus and uses
the read data to determine which button was pressed.
The PTT button is connected to the Patriot IC INT0 Interrupt pin for fast action of the Patriot IC to
execute the PTT operation.
Volume controls for the radio are set by up and down controls. These controls share the
UC_KP_COLUMN0, UC_KP_COLUMN1 and UC_KP_ROW7 lines. The Patriot IC uses these three
lines to determine whether the volume up or volume down button was pressed.
Figure 3-9 shows the buttons and controls implementation.