January 1990 5
Philips Semiconductors Product specification
Universal sync generator (USG) SAA1101
Lock modes
The USG offers four lock modes:
• Lock from the subcarrier
• Slow sync. lock, external H
ref
• Slow sync. lock, internal H
ref
• Fast sync. lock, internal H
ref
LOCK FROM SUBCARRIER
Lock from subcarrier to the line frequency for the above
mentioned TV systems is given below; the horizontal
frequency (fH) = 15.625 kHz for 625 line systems and
15.734264 kHz for 525 line systems.
These relationships are obtained by the use of a phase
locked loop and the internal programmed divider chain,
see Fig.3(a).
LOCK TO AN EXTERNAL SIGNAL SOURCE
The following methods can be used to lock to an external
signal source:
1. Sync. lock slow; the line frequency is locked to an
external signal. The line and frame information are
extracted from the external sync. signal and used
separately in the lock system. The line information is
used in a phase-locked loop where external and
internal line frequencies are compared by the same
phase detector as is used for the subcarrier lock. The
external frame information is compared with the
internal frame in a slow lock system; mismatch of
internal and external frames will result in the addition
or suppression of one line depending on the direction
of the fault. The maximum lock time for frame lock is
6.25 s, see Fig.3(b).
2. Sync. lock fast. A fast lock of frames is possible with a
frame reset which is extracted out of the incoming
external sync. signal, see Fig.3(c).
3. Sync. lock with external reference. Lock of an external
sync. signal to the line frequency with an external line
reference to make possible a shifted lock. The
SECAM (1 and 2) 282f
H
PALN 229.2516f
H
NTSC (1 and 2) 227.5f
H
PALM 227.25f
H
PAL B/G 283.7516f
H
subcarrier input is, in this case, used as an external
input for the horizontal reference, see Fig.3(d).
SELECTION OF LOCK MODE
Lock mode is selected using the inputs LM0 and LM1 as
illustrated in the Table below.
LM0 LM1 SELECTION
0 0 lock to subcarrier
0 1 slow sync. lock external H
ref
1 0 slow sync. lock internal H
ref
1 1 fast sync. lock internal H
ref