User Guide

PAMS
Technical Documentation
NME–3
Technical Information
Page 38
Issue 1 10/99
Backlight Dimming
The Backlight dimming is used to synchronise the dimming of all
backlights inside the cars cockpit. The Backlightdimming signal is a PWM
modulated signal that is delivered from the car to the GM8B.
Table 16. Backlight dimming
Parameter max typ min Notes
High voltage 16V 13.5V 9V
pulsewidth 100% 18% for supplyvoltage < 13 V
pulsewidth 100% 13% for supply voltage < 16 V
frequency 120 Hz 60 Hz
Rise and fall times dV/dt
dI/dt
200
mV/ms
20
mA/mS
The Backlight dimming signal is inverted by an transisitor and then routed
through an single gate inverter, to provide the following Lowpassfilter with
an symetrical Push–Pull driver. The Lowpassfilter has a corner frequency
of 0.1, to provide the ADC of the CCONT with the DC voltage that is
proportional to the Dutycycle of the Backlight dimming signal. The
information about the Duty cycle will be transfered as an M–Bus message
to the Handset in order to dim the LEDs in the Handset.
When an unprogrammed module is powered up the first time the MCU
starts from the boot rom inside the MAD2. The MBUS line is to be kept
low to inform the MCU that the flash prommer is connected and the MCU
should stop after the boot and wait for a download code.
When the flash programming is performed successfully the MCU switches
to flash prom software. If the baseband is powered up for the first time the
MCU will remain in local mode as the factory set has not been executed.
To allow re–programming of working modules the MCU is at startup forced
into local mode by connecting the MBUS to GND.