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PDF M494B1 Data sheet ( Hoja de datos )

Número de pieza M494B1
Descripción SINGLE-CHIP VOLTAGE TUNING SYSTEM WITH 4 ANALOG CONTROLS AND mP INTERFACE
Fabricantes ST Microelectronics 
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M494
SINGLE-CHIP VOLTAGE TUNING SYSTEM WITH
4 ANALOG CONTROLS AND µP INTERFACE
. NON-VOLATILE MEMORY FOR 20 PRO-
GRAM WORDS (17 BIT x 20)
- TUNING VOLTAGE 12 BITS
- BAND 2 BITS
- MULTI STANDARD 2 BITS
- PROGRAM SKIP BIT 1 BIT
- 10,000 MODIFY CYCLES PER WORD
- MIN. 10 YEARS DATA RETENTION
. 13 BIT VOLTAGE SYNTHESIZER (BRM + PWM)
. NV MEMORY FOR 4 ANALOG CONTROLS
(6 BIT x 4)
. 4 BAND SWITCH OUTPUTS
(VHF I & III, UHF, CATV)
. 5 x 7 KEYBOARD
. 2 AUDIO VISUAL OUTPUTS (VCR & PC)
. 2 CODED MULTI STANDARD OUTPUTS
(e.g. PAL, SECAM, NTSC etc.)
. DIRECT 11/2 DIGIT 7 SEGMENT COMMON
ANODE LED DISPLAY DRIVING
. PCM REMOTE CONTROL RECEIVER
(M708 transmitter)
. 5-BIT DATA INPUT + CONTROL LINE FOR
P INTERFACE
. LINEAR AFC DEFEAT OUTPUT
. FLYBACK/SYNC. COINCIDENCE INPUT FOR
SEMI-AUTOMATIC SEARCH
. STANDBY OUTPUT
. OPTION SELECT : 16 OR 20 PROGRAMS
. POWER UP MODE
. PROGRAM SKIP DEFEAT
. AV OPTIONS
. 1 * OR DECADE MODE OPTION IN 20 PRO-
GRAM OPTION
. TEMPORARY ANALOG UP/DOWN INDICA-
TOR ON LED DISPLAY
. BAND SKIP OPTION
. 455 TO 510kHz CHEAP CERAMIC RESONATOR
. VDD = 5V ± 5%. VPP = 25V ± 1V
pable of including a floating gate NV memory cell
(EEPROM).
The i.c. has been designed as a complete digital
TV tuning system based on the voltage synthesis
principle and as a replacement for all the conven-
tional potentiometers and band switches particu-
larly in low cost TV sets. It also provides some
functions normally only associated with higher cost
sets. NV memory is integrated on the chip together
with all the necessary control circuitry to providethe
program memory. Separate NV memory is also
integrated to provide the memory for four analog
controls. A seven segment LED display can be
directly driven by the chip to display the program
selected, and the direction of movement of the
analog controls. Provision is made for a remote
control receiver both on and off chip, the latter is
interfaced via a data input and single control line.
(This enables control by a microprocessor). A local
keyboard can be used with the device in a variety
of configurations. An option select pin provides for
different program number options, power up op-
tions and skip associated functions. This device is
another significant step towards the complete inte-
gration of TV control circuitry.
The device is packaged in a 40 pin DIL plastic
package.
DIP40
(Plastic Package)
DESCRIPTION
The M494 is a monolithic LSI integrated circuit
fabricated in SGS-THOMSON’s EPM2 process ; an
N-channel, Planox, double poly MOS process ca-
ORDER CODE : M494B1
June 1991
1/22

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M494B1 pdf
M494
FUNCTIONAL DESCRIPTION (continued)
Figure 3
τ 1 = RC
τ 2 = Ri . C
1.5V
Several tests are performed on the signal :
a) Measurement of the pulse distance T (time
base synchronization).
b) Check of the bit positions relative to the time
base windows.
c) Check of the parity bit.
d) Check of the absence of pulses between parity
and stop pulses.
e) Check of the noise level. The receiver checks
the noise level for a time T after each pulse
detected.
If all these tests are successful the received word
is stored and decoded. If not it is rejected. The
transmission is terminated on reception of the end
of transmission (EOT) code or if the internal timer
measures a transmission interruption of more than
550ms. For more detail concerning the operation
of the RC receiver refer to SGS-THOMSON Tech-
nical Note No. 155 pp11-12.
The RC receiver and the local keyboard have the
same command source priority i.e. a local com-
mand is not accepted until a previously accepted
RC command has been completely executed and
the EOT code transmitted. Similarly if a local com-
mand is under execution then an RC command will
not be accepted. The RC truth table and com-
mands are shown on the next page.
Analog Control Outputs
Four analog control outputs are implemented to
provide for Volume, Brightness, Saturation and
Contrast from four 6 bit D/A’s. These D/A’s use the
Pulse Width Modulation technique to synthesize a
pulse train of constant frequency but variable pulse
width (PWM). Each output delivers a 7.8kHz
square wave whose duty cycle is variable in 63
steps. External RC filtering and level shifting is
required to realise a static DC voltage from the
pulse train. If the analog outputs are continuously
varied by command from the keyboard or data
command sources the outputs will change approx.
every 112ms (fck = 500kHz) or approx. every
102ms if the command is issued from the RC
command source. One analog control is specifi-
cally designed asa volume control as mute circuitry
is built in.
On start up reset the analog control outputs except
volume are enabled after a period of approx.
1.1 seconds. In the Standby and Off states all the
analog control outputs are pulled to logic LO.
The normalise command reads the contents of
each analog memory sequentially to its corre-
sponding counter and D/A output.
Tuning Output
The tuning voltage is generated from a 13 bit
counter. The program memory stores the 12 MSB’s
of the tuning word. The range of the AFC circuitry
is at least 3 bits so the LSB of the tuning counter
does not affect the resolution of tuning.
The contents of the counter are converted using a
PWM and a Bit Rate Multiplier (BRM) technique.
13 bits gives 8192 steps which yields a resolution
of approximately 3.9mV with a max. tuning voltage
of 32V. This corresponds to a resolution of about
75kHz in the UHF band. The 5 MSB’s of the tuning
word are converted using PWM and the remaining
8 bits using BRM. Thus as the tuning word in-
creases from all zeroes the number of pulsesin one
period increases to 256 with all the pulses being
the same length (to = 2µs). For values larger then
256 PWM conversion takes place where the num-
ber of pulses in one period stays constant at 256
but the width changes.
When the pulse width reaches 15to two successive
pulses ”link” together and the number of pulses
decreases (see Figure 4).
The pulse train is fed to an external low pass filter
to realise a DC voltage. The temperature depend-
ence of this system is predominantly the switching
times of the output pulses and as there are only a
maximum of 256 pulses in one period the tempera-
ture stability is very good.
In Standby and Off states the tuning output is pulled
to logic LO.
Figure 4
No OF PULSES
256
TUNING
1V 31V VOLTAGE
5/22

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M494B1 arduino
M494
FUNCTIONAL DESCRIPTION (continued)
Data Input
Shown below are the codes for the commands :
see Table 2.
lected only in a rolling sequence by the band se-
quence keyboard command. The sequence is as
follows : VHF III, UHF, VHF I, CATV.
The Data input will accept signals whose timing is
defined in Figure 6 and electrical characteristics
defined in the table of static electrical charac-
teristics. The EOT code must be transmitted after
each command after a min. period of 112ms.
Band Outputs
Four band outputs are provided for selection of the
signal band : VHF I & III, UHF and CATV. Band skip
logic is implemented so that by tieing the relevant
pin to VSS a band can be skipped in regions of no
transmission in that band. The bands can be se-
Multi Standard Outputs
Two coded multi standard outputs (or general pur-
pose TV system flags) are provided so that the TV
set can be designed for use in areas of more than
one transmission standard. This function requires
an external decoder to realise 4 different standards
e.g. PAL 1, PAL 2, NTSC, SECAM etc. The multi
standard sequence command available from the
keyboard gives a simple binary count at the two
outputs : 00, 01, 10, 11, 00 etc. In Standby and Off
states the multistandard outputs are pulled to logic
LO.
Table 2 : Data Commands
Command
Number
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Function
16 Programs
20 Programs
EOT
Program 1
Program 2
Program 3
Program 4
Program 5
Program 6
EOT
Program 1
Program 2
Program 3
Program 4
Program 5
Program 6
Program 7
Program 8
Program 9
Program 10
Program 11
Program 12
Program 7
Program 8
Program 9
Program 0
– 10 (decade)
+ 10 (decade)
Program 13
Program 14
Program 15
Program 16
Normalise
Volume up
1*
NOP
NOP
NOP
Normalise
Volume up
Volume down
Contrast up
Contrast down
Brightness up
Brightness down
Saturation up
Volume down
Contrast up
Contrast down
Brightness up
Brightness down
Saturation up
Saturation down
Memory Seq. up.
Memory Seq. down
On/standby (toggle)
Standby
Mute (toggle)
Saturation down
Memory Seq. up.
Memory Seq. down
On/standby (toggle)
Standby
Mute (toggle)
NO TRANSMISSION (pulled up)
Code
D0 D1 D2 D3 D4
00000
10000
10000
11000
00100
10100
01100
11100
00010
10010
01010
11010
00110
10110
01110
11110
00001
10001
01001
11001
00101
10101
01101
11101
00011
10010
01011
11011
00111
10111
01111
1111
The above table shown the difference between the 16 and 20 program options with respect to the Data input commands.
Commands 10, 11, 12 & 13 change function between the two options. Commands 14, 15 & 16 should not be used in the 20 program option,
as they have no function.
NOP = No operation.
11/22

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