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參數(shù)資料
| 型號： | M494 |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | SINGLE-CHIP VOLTAGE TUNING SYSTEM WITH 4 ANALOG CONTROLS AND mP INTERFACE |
| 中文描述： | 單片電壓調(diào)整系統(tǒng)，4模擬控制和MP接口 |
| 文件頁數(shù)： | 14/22頁 |
| 文件大?。?/td> | 223K |
| 代理商： | M494 |
FUNCTIONAL DESCRIPTION
(continued)
Manual Tuning
Manual tuning commands tune up or down, are
available from keyboard only and are provided to
allow both manual station search and tuning
adjustments. If a continuous tuning up or down
command is made from the keyboardthe speed of
movement of the tuning counter is as shown in
fig. 10 for the UHF and CATV bands.Time t
o
isthe
start time for the key being pressed. When the
FB/sync. coincidenceinput is a logic HI thetuning
speed is reduced to 16 steps/sec. If, at time t
o
the
FB/sync.coincidence input is at logic LO than the
tuning.sweep speed jumps immediately to 512
steps/sec.
For VHF III & I all these levels are shiftedup by a
factor of 2 & 4 respectivelygiving slowest speeds
of 8 steps/sec. and 16 steps/sec. and highest
speeds of 1024 steps/sec and 2048 steps/sec. If
the continuityof command is broken by releasing
the keyboard for example then the tuning speed
returns to its slowest speed when the FB/sync.
coincidenceinputis atlogicHI.Ifthe upperorlower
limitofabandisreachedduringmanualtuningthen
tuning will continue in the same direction from the
Figure10 :
Tuning Sweep Speed (UHF & CATV BANDS)
opposite limit after a 480ms delay to allow for the
dischargeof the external network.
The tuning counter is 13 bits in length giving a
range of 8192 steps. The UHF band has a band-
width of approx. 400MHz. Thus in the UHF band
the slowest speed of 4 steps/sec. gives a tuning
speed of about 200kHz/sec. The fastest speed of
512 step/sec. corresponds to a total band sweep
time of 16 seconds.
Program Memory Sequence
Acontinuousup/downprogrammemory command
from keyboardproduces a program change every
500ms. From remote control and data command
sources a continuousprogram memory sequence
command produces a program change approx.
every 500ms or every 5 received commands. A
memory sequence up or down command issued
from anysourcewill bringthe deviceout ofstandby
to the programselected before standby was com-
manded. The memory sequence up or down will
not then commenceuntil the command is stopped
and reissued from any source (until an EOT has
been received or internally generated).
512
4
8
16
32
FB/SYNC.
COINCIDENCE
FB/SYNC.
COINCIDENCE
FB/SYNC.
COINCIDENCE
Time (sec)
t0
1
2
3
TUNING SWEEP
SPEED (STEP/SEC)
4
M494
14/22
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