GRUNDIG T55830MULTI/COM
Instrukcja Serwisowa

10 GRUNDIG Service
IR-interface directly into the PLD (pin20). TVled interface TV-OFF (with switch) TV-ON TV-STANDBY TV-MESSAGE OFF ON OnBoardled interface MasterModem. Buzzer/Audio/Mute-interface possible revisions.

Allgemeiner Teil / General Section CUC 2003 H

iTV-Card / COM-Card
MegaText
Overview
The InfraRed from the TV is a TTL-level signal and will be buffered first before feeding to the MicroController (pin20) and the PLD (pin19). The IR-signal made by the MicroController (pin18) is fed The MicroController will be able to control the IR-signal flow with the IRecho-line (pin5). It is possible to echo all the incoming IR-signals from the TV directly back-to the TV (echo-mode), or to send MicroController IR-commands to the TV.

iTV-Card / COM-Card

In this application, the MegaText-chip (U1, SDA5273) is only used to generate overlay information for all the iTV on-screen menu�s. The TeleText decoding is being done by the TV and not by the MegaText-chip. For this OSD-application the SDA5273 is sufficient, but it is also possible to use the more expensive SDA5275 (pin-compatible, iTV-software supports both types). For future applications the MegaText-chip can decode Level 1.5 and 2.5 TeleText information. For level 1.5-TeleText decoding the SDA5273 can be used, but for full decoding of level 2.5-TeleText the SDA5275 + external DRAM must be used.

The MicroController has to control the TVled (pin36) which is in front off the TV. The following table shows the different states of the TV-led: NormalMode DIMMED FLASHING FactoryMode OFF DIMMED ON -----

Syncs The MegaText-chip will run in slave-sync-mode, this means that it will follow the incoming Vsync and Hsync-signals from the TV to synchronise the outgoing R/G/B/Blanking signals. The CVBS-signal supplied by the TV will not be used in this application because there�s no need for Video/TeleText-information. Another reason for the use of the separate H/V-syncs is that these syncs are on TTL-level and therefore easy to use instead of separating sync-information by clamping and data-slicing of the incoming CVBS-signal.

The TV-OFF state will be monitored by CN1, pin3. When the TV is off this pin has a voltage of 0Volt, and in all other states there�s an unregulated DC-voltage of 13.5-14.5Volt. This signal will be regulated to 4.7Volt by a zener-diode (D9) and fed to the MicroController (pin33).

Overlay The overlay will be controlled by the BLANKING-output-pin of the MegaText. This is an OpenDrainoutput and displays the RGB-information when BLANKING is high. When BLANKING is low, there�s no
The two LEDs onboard will reflect the state of FSK-communication. The REDled (pin32) will be used to show if there�s a MasterModem in the system (ON), and the green one (pin39) is ON when the card is actually polled by the MasterModem. This means that when the Redled is ON and the GREENled is OFF that the card is not being polled by the

overlay and the TV�s internal source will be displayed on the screen.

Memory The MegaText has sufficient onboard-memory for the current application. For future applications an external DRAM (U2) can be placed on the PCB. This optional DRAM can have the size of 256K, 1M, 4M or 16Mbit.

The Buzzer will be controlled by the MicroController (pin19) with a square-wave of a certain frequency. This pin is also connected to CN4, pin1 to give exactly the same signal to the TV. The Mute-out will be controlled by the MicroController (pin37) with an open-collector output-stage.

Signals The signals between the TV and the MegaText-chip are: CVBS (pin10)

ChassisID/HardwareID-interface With a dipswitch of four contacts (SW1) it�s possible to select the chassis-number of the TV. The MicroController reads this information (pins34, 35, 36 and 39) after PowerUp or a Reset. In this way 16 different chassis-numbers can be selected.

VSYNC (pin4) HSYNC (pin5) RED (pin61) GREEN (pin62) BLUE (pin63) BLANKING (pin64)

In the same way, only with resistors connected to GND instead of a dipswitch it�s possible to give the card a hardwareID. Three pins (pins 4, 14 and 15) are reserved for this purpose to give a total number of 8

The R/G/B gain and DC-level can be adjusted by the MegaText internal-registers (software-controllable).

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