Service manualCHASSIS 2112-Series EC7-A
Functionality.Input (I)ActivPinPinRelated
or Outputenumbernumbersignal.
(O)Level(ST92195)(ST92185)
TXT microNot TXT
BG system selectionOL4228CF1
DK system selectionOL4329CF2
Elimination of AGC feature duringOL4430-AGC_LS
automatic tuning
LB band selectionOL4531-LB
MB band selectionOL4632-MB
AlarmOPWM 4733BEEP
HB band selectionOL4834-HB
Width adjust output (optionalOPWM 4935WIDTH
circuit)
Sound muteOH5238MUTE
O: Led controlI/OL5339LED
I: Production test communication
Tuning voltageOPWM 5440VTUNE
Infrared receptor signalI5541IR
Keyboard signalIA/D5642KEY
4.2.2 Supply.
The number of supply pins depends on the version (with TXT or without TXT). A list of supply pins is shown in the
attached table, indicating the number and the name of the pin.
Supply pin namePin number (Micro with TXT,Pin number (Micro without
ST92195)TXT, ST92185)
VDD2121
AVDD325---
AVDD231---
AVDD13925
Where:
VDD !!!! CPU supply (+5V_M).
AVDD1, AVDD2 !!!! Analogic supply (+5V_M).
AVDD3 !!!! Analogic supply (connected internally to AVDD1 and AVDD2).
4.2.3 Oscillator.
The oscillator is based on a quartz crystal of 8MHz (X100), which is connected to 50 and 51 pins (ST92195) or to
the 36 and 37 pins (ST92185). It must oscillate whenever the +5V_M is present.
4.2.4 Reset.
This signal is active at low level. It initialises the microprocessor (whenever the supply is correct). Q858 and his
periphery generate the reset signal. The reset is active when the B2 voltage is lower than 7.4 volts (approximately).
4.2.5 RGB output, character generator.
A character generator is integrated into the microprocessor. The outputs are RGB (pins number 17,16,15) and Fast
Blanking (pin number 18). These outputs are active when the OSD or the TXT are present.
4.2.5.1 Character generator synchronism.
SignalPin number (Micro with TXT,Pin number (Micro without
ST92195)TXT, ST92185)
VSYNC4127
HSYNC 4026
The character generator synchronisation is done with the VSYNC and H_FLY&SYNC signals.
The H_FLY&SYNC signal is used to synchronise horizontally the character generator. It is generated from the main
flyback and it is AC coupled. At the Q651 emitter, there are 8 Vpp line frequency pulses synchronized with the main
flyback. The horizontal position can be adjusted in the service menu.
The VSYNC signal is used to synchronise vertically the character generator. The information comes from the
vertical retrace pulses generated by IC701.
4.2.5.2 RGB output voltage.
The RGB signals amplitude is 1V maximum. The Fast blanking output (VDS) amplitude is approximately 3V.
4.2.6 Teletext (only for ST92195 version).
The ST92195 microprocessor has a teletext decoder integrated. The parts of this circuit are Data slicer, decoder,
memory (1 page) and character generator.
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