Motorola GM160 Service Information - Page 13

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Also for Motorola GM160: Service Information (34 pages), User Manual (44 pages), Basic Service Manual (46 pages), Service Information (32 pages), User Manual (44 pages)

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Controlhead Model for GM160, GM360 and GM660

includes the RAM start address for the following display data. With input A0 set to logic „1" the µP

then writes the display data to the display RAM. When data transfer is complete the µP terminates

the chip select, RD and WD activities.

The display driver's power circuit provides the voltage supply for the display. This circuit consists of a

voltage multiplier, voltage regulator and a voltage follower. The external capacitors C0971 - C0973

conﬁgure the multiplier to double the supply voltage. In this conﬁguration the multiplier output VOUT

(U0971-8) supplies a voltage of -5V (2* -5V below VDD). The multiplied voltage VOUT is sent to the

internal voltage regulator. To set the voltage level of the regulator output V5 (U0971-5) this voltage is

divided by the resistors R0973 and R0974 and fed back to the reference input VR (U0971-6). In

addition the regulator output voltage V5 can be controlled electronically by a control command sent

to the driver. With the used conﬁguration the voltage V5 is about –2V. The voltage V5 is resistively

divided by the driver's voltage follower to provide the voltages V1 - V4. These voltages are needed for

driving the liquid crystals. The level of V5 can be measured by one of the µP's analogue to digital

converters (U0831-20) via resistive divider R0975, R0976. To stabilize the display brightness over a

large temperature range the µP measures the temperature via analogue to digital converter (U0831-

18) using temperature sensor U0834. Dependent on the measured temperature the µP adjusts the

driver output voltage V5, and in turn the display brightness, via parallel interface.

3.8

Microphone Connector Signals

Signals BUS+, PTT IRDEC, HOOK, MIC, HANDSET AUDIO, FLT A+, +5V and 2 A/D converter

inputs are available at the microphone connector J0811. Signal BUS+ (J0811-7) connects to the

SBEP bus for communication with the CPS or the Universal Tuner. Line MIC (J0811-5) feeds the

audio from the microphone to the radio's controller via connector J0801-4. Line HANDSET AUDIO

(J0811-8) feeds the receiver audio from the controller (J0801-6) to a connected handset. FLT A+,

which is at supply voltage level, and +5V are used to supply any connected accessory like a

microphone or a handset.

The 2 A/D converter inputs (J0811-9/10) are used for a microphone with keypad. A pressed key will

change the dc voltage on both lines. The voltages depend on which key is pressed. The µP

determines from the voltage on these lines which key is pressed and sends the information to the

host radio.

Line PTT IRDEC (J0811-6) is used to key up the radio's transmitter. While the PTT button on a

connected microphone is released, line PTT IRDEC is pulled to +5 volts level by R0843. Transistor

Q0843 is switched on and causes a low at µP port PA2. When the PTT button is pressed, signal PTT

IRDEC is pulled to ground level. This switches off Q0843 and the resulting high level at µP port PA2

informs the µP about the pressed PTT button. The µP will inform the host radio about any status

change on the PTT IRDEC line via SBEP bus.

When line PTT IRDEC is connected to FLT A+ level, transistor Q0821 is switched on through diode

VR0821 and thereby pulls the level on line ON OFF CONTROL to FLT A+ level. This switches on the

radio and puts the radio's µP in bootstrap mode. Bootstrap mode is used to load the ﬁrmware into the

radio's ﬂash memory (See controller sub section for more details).

The HOOK input (J0811-3) is used to inform the µP when the microphone´s hang-up switch is

engaged. Dependent on the CPS programming the µP may take actions like turning the audio PA on

or off. While the hang up switch is open, line HOOK is pulled to +5 volts level by R0841. Transistor

Q0841 is switched on and causes a low at µP port PA1. When the HOOK switch is closed, signal

HOOK is pulled to ground level. This switches off R0841 and the resulting high level at µP port PA1

informs the µP about the closed hang up switch. The µP will inform the host radio about any status

change on the HOOK line via SBEP bus.

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