Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV set- Control of LED’s for operating and standbydisplay.- Creation of further switching processes,e.g. ON/OFF, AV transfer, etc.- Simulation of a clock synchronised by VPSinformation.- Timer function for programmable disconnecttime and recording timer.- Code converter for IR commands for theremote control of a video recorder via theAV voltage switching line and the Dolbysurround unit.- RS 232 for communication with the onlineas well as the DVB module.- Digital Link Plus Control for the 3Euro/AV socketsIn order to fulfil the required tasks the followingcircuit components are combined in onechip:- C 16 core with CPU and interrupt controller- 2 kByte XRAM as working memory- Interface for the external ROM- Quarz controlled clock generator- Interface for the three I2C buses- Multifunctional timer- IR decoder- ON/OFF Flip-Flop- Reset circuit for internal reset- Reset circuit for external IC’s.- Ports P2 to P6 with 44 input and outputpins.Many of these functions are implemented notby the hardware of the processor, but by theLoewe-specific software.4.1.4 ResetFor correct functioning of the device, variousreset pulses are necessary. The first requiredis a reset on pin 73 for the SDA 6000, as soonas its operating voltage U3.3 is available andthe 6 MHz system cycle has run. This reset isproduced by I 2941. After this reset the SDA6000 starts to operate and implements andemits control commands.The microprocessor also has a reset on pin 8,produced by I 2946, if the circuit power supplyhas run and all IC’s have an operating voltage.This reset is retarded in SDA 6000 andthen emitted from pin 100 to the digital IC’s.RESET digital component input pin 8The reset for this input is formed by a steeppositive flank. As U3,3 is the last voltageswitched by the power supply unit, this reset iscoupled to the voltage. The reset pulse is createdin I 2946 and is present on pin 8 of themicroprocessor, if all IC’s in the chassis havean operating voltage. SDA 6000 can then begincontrolling the IC’s. In addition the processoralso reacts, if the reset is not present onpin 8 or during operation. Normally 5 V is alwaysfelt on a reset input, provided the deviceis fully switched on.RESET digital component output pin 100Via this pin the microprocessor sends the resetto the other circuits. This is coupled to inputpin 8. In this way the processor can monitorthe reset, and for transient voltage failurescan prevent, the level on the reset line collapsing.On the other hand, the circuit alsomakes it possible for the SDA 6000 to emit asoftware controlled reset on pin 50 during operationIn standby and on start up L level is initiallyfelt on pin 100. Not until the SDA 6000switches pin 100 to H level, does the L/H flankproduce the reset for the IC’s. During operationthe reset inputs must be held permanentlyat H level, otherwise the working register willbe deleted.Document Q 2500 67 © Loewe ProCollege