ST92195C STMicroelectronics, ST92195C Datasheet - Page 164

• Manufacturer Part Number: ST92195C
• Description: 48-96 Kbyte Rom Hcmos Mcu With On-screen Display And Teletext Data Slicer
• Manufacturer: STMicroelectronics

TELETEXT SLICER AND ACQUISITION UNIT (Cont’d)
TELETEXT SLICER INITIALIZATION REGISTER
(TXSLIR)
R249 - Read/Write
Register Page: 35
Reset Value: 0000 1011 (0Bh)
Bits 7:6 = Reserved bits. Keep in reset state.
Bit 5:0 = INI(5:0): 6-bit initialization value of the
Slicer DAC. This value is used to re-initialize the
Slicer DAC at each beginning of TV line.
PRE-AMPLIFIER AND ADC SELECT REGISTER
(PASR)
R255 - Read/Write
Register Page: 35
Reset Value: 0000 0000 (00h)
Bits 7:3 = Reserved bits, keep in reset state.
Bit 2 = PREAMP: Preamplifier enable.
This bit is set and cleared by software to define the
analog CVBS input configuration of the Teletext
slicer.
0: Activate on-chip pre-amplifier providing to the
1: Pre-amplifier is by-passed.
Teletext front-end Slicer an amplified CVBS sig-
nal, the gain being defined by the TXTGC(1:0)
bits of the Teletext Slicer Control Register (TX-
SCR).
0-
7
7
0
0
0
INI5
0
INI4
0
INI3
0
PRE-
AMP
INI2
ST92195C/D - TELETEXT SLICER AND ACQUISITION UNIT
INI1
0
ADC-
INI0
SEL
0
0
Bit 1 = Reserved bit, keep in reset state.
Bit 0 = ADCSEL: ADC Selection.
This bit is set and cleared by software to choose
which analog signal is sent to the A/D converter
channel 0.
0: Channel 0 is connected to the VDETB signal
1: Channel 0 is connected to the VBGP signal (on-
The Sync pulse amplitude seen at the CVBS1 pin
can be easily determined calculating the differ-
ence of 2 A/D conversions, converting first the
VDETB signal and then the VBGP signal (the max-
imum code FFh represents a 1V amplitude).
VsyncAmp= (N
For an ideal composite video signal, the theoreti-
cal gain to program with the TXTGC(1:0) bits is:
Gth= 0.4 / VsyncAmp (V)
(amplitude of the sync pulses extracted from the
CVBS signal).
chip analog reference voltage).
VDETB
-N
VBGP
)/FF Volt
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