Chroma Id - Sanyo C21ZM45 Training Manual

2-4 Chroma ID
The identification of a colour or black/white broadcast is achieved by sensing the voltage
level input at pin 20. This voltage is supplied from pin 26 of ICI 01 through the inverter circuit,
Q719. When there is a black/white broadcast the voltage on pin 26 goes low.
Normally, pin 26 operates as colour control function, and the control voltage is from pin 4 of
the CPU.
To identify the colour system during a black/white broadcast, the CPU judges that the system
is NTSC when the following conditions are detected at same time.
(1) The colour system is "AUTO" or "NTSC" system.
(2) The field frequency is 60 Hz.
(3) TV/AV mode is "TV" mode.
CPU
Pin20 Judgement
L
Colour broadcast
[H I BW
broadcast I
20
—
i
R778
5.6k
AA
,.
R778
5.6k
t
C742
1
Colour control from pin4 of
CPU A
ICI 01
Chroma/Def.
26
2-5 Ident (Identification)
The identification of the receiving signal status is done by the CPU sensing the voltage level
at the input pin 15, as shown below. The ident signal is presented at pin 4 of IC101 and fed to
pin 15 of the CPU through the converter circuit consisting of Q708, R765 and R764.
When the CPU judges that the system is 4.43MHz, it outputs a "Low" signal from pin 40 to
select PAIJSECAM system.
CPU
15
4C
Q
8V
I
Iclol
Chroma/Def.
Q708
R767
100
w
4
Y&"
I
:::: I I
10k
C718
C132
0.01 0.1
Pin40 Pin15
Judgement Signal status
L
O-1.8V
4.43 MHZ No sync.
H
1.8V - 4.3V 3.58 MHz
Signal present
L
4.3 v - 5.OV 4.43 MHZ Signal present
I
_.
A7-A
-12-
A7-A