3-50 Theory of Operation: Controller
3.2.6 User Interface
3.2.6.1 Control Top
The control top contains an On/Off & Volume Knob (S3), a sixteen-position Channel/Frequency
Switch with programmable concentric two-position switch (S2), a three-position (A,B,C)
Programmable Toggle Switch (S4), and an orange programmable Top Button (S1). The Control Top
also includes a TX/RX LED that is solid amber upon receive, red on PTT, and blinks amber on
secure TX/RX. Additionally, the Control Top includes a transflective FSTN display. Control Top
components are mounted on a flex circuit which connects to controller board connector J2101.
When the On/Off & Volume Knob (S3) is switched to the 'ON' position, the switch is grounded and
MECH_SW is pulled low. MECH_SW is an input to MAKO (U15). The logic low input enables an
external FET (Q2) gate voltage, FET_ENX, which switches UN_SW_B+ to SW_B+ and turns the
radio on. Volume is also controlled through S3 and is an input to MAKO. The VOL signal is
connected to a potentiometer biased between ground and 2.775 V (R246) from MAKO. When the
volume knob is turned, the VOL signal level is converted to a code word by MAKO's ADC and read
by OMAP through SPI.
Switch S4 is the three-position, binary-coded, toggle switch typically used for expanded Zone/
Channel Selection. Two outputs of the switch,TG0 and TG1, are biased to 1.875 V. The third output
is grounded. Two-bit codewords from the switch are read by OMAP through the CPLD's EMIFS
interface and indicate which of the three positions is set.
The orange programmable Top Button (S1) is typically used for emergency. It is also biased to
1.875 V (R140) and is an input (EMERG_PB) to the CPLD. A button press is detected when
EMERG_PB is pulled low.
Like the three-position switch, the Frequency Switch (S3) is also binary coded. S3's output pins are
connected to GPIO pins of the CPLD which provide a four-bit binary word (signals FREQ_SEL_0,
FREQ_SEL_1, FREQ_SEL_2, and FREQ_SEL_3) to OMAP indicating which of the 16 pins of the
switch is set. This switch provides an additional output, SEC_CLEAR, which is typically used for
coded or clear mode selection. Selecting clear mode pulls this signal to a logic low, and it can be
monitored from R2.
Figure 3-40. Control Top Block Diagram
CPLD
Frequency Switch
ABC
Toggle
Switch
Concentric
ON/OFF SW
Volume POT
Emergency
Switch
MAKO
Top
Display
TX/RX
LED
Intelligent
Lighting
OMAP
FPC Vocon Bd
pg
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