MC44BC374 MOTOROLA [Motorola, Inc], MC44BC374 Datasheet - Page 18

• Manufacturer Part Number: MC44BC374
• Description: PLL Tuned PAL/NTSC UHF and VHF Audio/ Video High Integration Modulator IC
• Manufacturer: MOTOROLA [Motorola, Inc]

Modulator Operation
13.7 Test Pattern Generator
The IC generates a simple test pattern, which can be switched under bus control to permit a TV receiver to
easily tune to the modulator output. The pattern consists of two white vertical bars on a black background
and a 976Hz audio test signal.
13.8 PLL Section
The reference divider is a fixed divide-by-128, resulting in a reference frequency of 31.25KHz with a
4.0MHz crystal. The 31.25KHz reference frequency is used for both UHF and Sound PLLs.
The prescaler is a fixed divide-by-8 and is permanently engaged.
The programmable divider division-ratio is controlled by the state of control bits N0 to N11.
The divider-ratio N for a desired frequency F (in MHz) is given by:
with:
13.9 UHF Oscillator — VHF range
The UHF oscillator is fully integrated and does not require any external components.
For low frequency testing or VHF range operation (test mode 1, states 1.b to 1.c), the UHF oscillator can
be internally divided by: 2, 4, 8, or 16.
13.10 Differences From MC44BC374C device
18
•
•
•
•
•
•
“OSC” bit programming is inverted
Start up channel is ‘71’ instead od ‘36’
Hardware standby mode is added
Logic Output Port is not available
“TB1” bit is not available (limited software compatibility with the MC44355 device)
Read Mode is not available
N
0
TE1
=
TE2
2048 N11
10
×
MC44BC374T1 Technical Data
+
20
1024
24 28
×
N
N10
30
TIME IN µS.
=
F
-- -
8
+
×
……
128
-------- -
40
4
+
44
4 N2
×
7/10
50
+
2 N1
3/10
×
60
+
64
N0
MOTOROLA