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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)： | 13/22頁 |
| 文件大?。?/td> | 223K |
| 代理商： | M494 |
FUNCTIONAL DESCRIPTION
(continued)
Skip Function
Program skip is implemented in the M494 by a
single memory bit associated with each program
word.The bitactsasa flagto thedeviceto indicate
that the programword shouldbe skipped and the
next program word read from the memory in as-
cending or descendingorder if the skip flag is set.
Programs are skipped only when accessed using
the memorysequenceup/downcommands.Direct
accesstoaprogramfrom thekeyboard,RCordata
command sources will always override the skip
function. e.g. if skip is set on prog. 7 and prog.7 is
commanded from RC then prog. 7 will be tuned
even if there is nc prog. stored in that memory
location.
In order to program the skip bit and to defeat its
function when required two commands are avail-
able : set skipflag andskip defeat.The skip defeat
switch is designed to be activated by a facia panel
on the TV set under which are infrequently used
controls.
On the set skip flag command the M494 storesthe
current contentsof thetuning,bandandMS count-
ers and setsthe skip bit. After the set skip flag
operation the contentsof thetuning, band and MS
counters will not change and the device continues
to output these values. The operationis transpar-
ent to the user in termsof functionbut is indicated
on the display by the program number flashing at
5Hz for 1 second. In order to reset the skip bit for
any programword the desired program should be
selected with skip defeated. A station shouldthen
be tuned,if required, andthen the store command
issued. The store command automatically resets
the skip flag.
The skipdefeatcommandenablesthereadingand
writing(plusresettingof skipflag)of memorywords
whose skip flag is set. If skip isdefeatedthe device
will only access the number of programs selected
by the option select i.e. If 16 programs only are
selected then skip defeat will NOT enable access
to all20 programs.
Reset
There are twoconditionsunderwhich the M494 is
reset : power on and start up (On command).
Power on reset is triggered whenever V
DD
falls
below about 3V.
The duration of this reset is 110ms after V
DD
has
been restored.
Power On Reset
(Powered down to Off or Standby states)
After the reset period of 110ms:
a) The programcounter is set to program1.
b) The outputs are disabled as defined in the Off
and Standby states. See Standby & Off
definitions.
c) The option selection, keyboard, momentary on
switchand,wheninstandby,thedisplay, RCand
data inputs become active. For the ”activity
level” of the keyboardinOff andstandbystates.
SeeStandby & Offdefinitions.
d) An internal register is set to indicate that the
devicehas powered up from the powereddown
state.
Start Up Reset
(Standbyor Off states to Onstate)
Astart upreset is instigatedby thereceptionof the
commands given in the definition of terms or the
Standbysection.
The followingthen occurs :
a) The internal register indicating that the device
has powered up from the powered down state
is read :
I) If the register is set than the memory word
addressedby the program counter is loaded
into the tuning counter and then the analog
valuesare read rom the memory.
II) If the register is reset then the previously
selected tuning and analog values are left
unchanged.
b) The AFC is defeatedand the volume muted for
a period of approx 1.7 secondsor 0.6 seconds
longerthan the other analogoutputs.
c) The tuning and analogue outputs, except
volume,are enabledafter approx.1.1 seconds.
d) The volume output is enabledafter 1.7 seconds
e) The standby output is pulled up internally to
logic HI
f) The internal register is reset.
If the device has either of the power up options
(power up in Off orstandby states)selected then it
willperformapowerupresetbutalltheoutputsand
commandsourceswillremain disabled,thenonthe
On command,a start up reset will be performed.If
the device is required to power up in the On state
using the momentary mechanical switch con-
nectedto theh+i pin thenitwill performanordinary
power on resetfollowed immediately by a startup
reset. The outputs and command sources will be
enabledafter the periods definedabove.
M494
13/22
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