Remote Control Technical Specifications

JVC uses a "space-width" codification, it seems to be a standard in Japanese remotes.

Lets consider the smaller time as T, measuring 560 microseconds.

Each transmited bit is composed by +T -T for bit zero or +T -3T for bit 1.
So, bit zero has a length of 1120us, while bit 1 is 2240us.

                                                                Figure 1

The UP level (+T) on the above signal means infrared being transmitted
by 36kHz carrier, while the DOWN level means silence.

If you hook up an infrared Module Sensor, you will see this waveform
inverted at its output, since its output goes DOWN in presence of
infrared carrier of 36kHz.

Well, lets see the DATA Frame:

  START      SYNC        ADDRESS (8 BITS)        COMMAND (8 BITS)   
16T              7.5T                LSB             MSB                   LSB                   MSB
                                                                Figure 2

First it is transmited a Start, long 16T active 36kHz infrared, it is around
9ms time (16T) and it is used to wake-up the receiver.

The Start is followed by 4.3ms of silence, it is about 7.5T time. This odd
time is what identifies the frame, or a Data Frame or a Repeat Frame.

4.3ms or 7.5T time means DATA Frame.

Then follows 16 bits of data, broken down in 2 bytes of 8 bits.

The first 8 bits is the Address, first bit is the LSB.
The second 8 bits is the Command, first bit is the LSB.

Below an example of the transmission package:

                                                                Figure 3

The Start and Sync above are out of proportion for 16T and 7.5T when
compared to a single T, but it is just for understanding.

If you keep pressed a remote key, this Japanese codification will not
be repeating the DATA Frame as the Sony or RC5 coding do, instead
it first send just once the DATA Frame and then it keep transmiting a
REPEAT frame every 110ms:

                                                                Figure 4

The REPEAT Frame consist of again the Start (16T) pulse, followed now
by a different Sync Silence of only 4T (in the DATA Frame it is 7.5T), then
by a single pulse of T time.   This REPEAT frame will keep repeating
itself each 196T time or 110ms, until you release the remote key.
As the REPEAT Frame uses only 17T active infrared power, so it uses
only 17/48 of the DATA Frame power, saving 65% of battery power
while you keep a key pressed.

The REPEAT Frame is identified by the Sync of only 4T.
The DATA Frame is identified by the Sync of 7.5T.

The following procedure to detect and identify the code, will work
with ANY microcontroller / microprocessor.

1)  Set Var1 = 128,  Var2 = 0

2)  Start by waiting the signal to go DOWN - This will be the START Bit.

3)  Wait for the signal to go UP - This should take about 9ms to happens.

4)  You are in the Sync Time.
     This should take about 4.3ms if DATA Frame or 2.25ms if REPEAT frame.

5)  Wait for the signal to go DOWN

6)  Here you are in the IR active time, bit start pulse.
     Wait for the signal to go UP.

7)  Here you are in the silence period, where it will decide if the bit is 0 or 1.
     Now Wait 800 microseconds.

8)  Measure the Signal Level.

     If the level is DOWN, then the Transmitted Bit is Zero, since the previous
     bit already  finished and the new bit already started. Then you should do:
     -  Set Carry Bit Zero
     -  Rotate Right Var1
     -  Rotate Right Var2
     -  Check Carry Bit - If On then Goto End.  If Off then Go back to step [6]

     If the level is UP, then the Transmitted Bit is ONE, since the previous
     bit didn't finished yet and you are in the 3T time. Then you should do:
     -  Set Carry Bit ONE
     -  Rotate Right Var1
     -  Rotate Right Var2
     -  Check Carry Bit - If On then Goto End.  If Off then Go back to step [5]
By doing this sequence, you only need a timming routine of 800
microseconds, and don't need to measure individual bits.

Observe loaded VAR1 with value 128 (binary 10000000) at entry, this bit will exit
into Carry only after 32 times "Rotate Right  Var1, Var2 since there are
16 bits to be shifted left to this happen.  It is used as a Rotation Left Counter.

List of Var1/Var2 read from the
JVC Remote Control RM-SMXK3A
Compu-Play Control

Command : Address    Description
-------   -------    -----------

21:A3    1
22:A3    2
23:A3    3
24:A3    4
25:A3    5
26:A3    6
27:A3    7
28:A3    8
29:A3    9
2A:A3    10
2F:A3    +10
17:A3    STBY/ON
03:A3    SLEEP
3E:A3    AUX
0B:A3    FM/AM
5F:A3    FM MODE
79:B3    CD1
7A:B3    CD2
7B:B3    CD3
4C:B3    CD |>
58:9F    TAPE A/B
0F:83    TAPE |>
18:A3    |<< REWIND
19:A3    FFORWARD |>>
71:9F    STOP
1E:A3    VOL+
1F:A3    VOL-

If you want to have your Sony remote control read and posted here, send it to our mail address
posted at the home page. If you want your remote back, please send $3.95 in stamps along with
the remote, so we'll ship it back to you via priority mail (don't forget to include your name and mail
address). If you have a list of your Sony remote control codes  just email me it, I will post it here..

Wagner Lipnharski - UST Research Inc - March/2002

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