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M3004LD

REMOTE CONTROL TRANSMITTER

STMicroelectronics 

M3004LAB1 - M3004LD

REMOTE CONTROL SIGNAL OUTPUT (REMO)

The REMO signal output stage is a push-pull type.

In the HIGH state, a bipolar emitter-follower allows

a high output current. The timing of the data output

format is listed in tables 1 and 2. The information is

defined by the distance tb between the leading

edges of the flashed pulses or the first edge of the

modulated pulses (see Figure 3). The format of the

output data is given in Figures 2 and 3. The data

word starts with two toggle bits T1 and T0, followed

by three bits for defining the sub-system address

S2, S1 and S0, and six bits F, E, D, C, B and A which

are defined by the selected key.

In the modulated transmission mode the first toggle

bit is replaced by a constant reference time bit

(REF). This can be used as a reference time for the

decoding sequence. The toggle bits function is an

indication for the decoder that the next instruction

has to be considered as a new command. The

codes for the sub-system address and the selected

key are given in tables 3 and 4.

The REMO output is protected against ”Lock-up”,

i.e. the length of an output pulse is limited to < 1ms,

even if the oscillator stops during an output pulse.

This avoids the rapid discharge of the battery that

would otherwise be caused by the continuous ac-

tivation of the LED.

OSCILLATOR INPUT / OUTPUT

(OSCI and OSCO)

The external components must be connected to

these pins when using an oscillator with a ceramic

resonator. The oscillator frequency may vary be-

tween 350kHz and 600kHz as defined by the reso-

nator.

FUNCTIONAL DESCRIPTION

Keyboard operation

In the stand -by mode all drivers (DRV0N to

DRV6N) are on (low impedance to VSS). Whenever

a key is pressed, one or more of the sense inputs

(SENnN) are tied to ground. This will start the

power-up sequence. First the oscillator is activated

and after the debounce time tDB (see Figure 4) the

output drivers (DRV0N to DRV6N) become active

successively.

Within the first scan cycle the transmission mode,

the applied sub-system address and the selected

command code are sensed and loaded into an

internal data latch.

In contrast to the command code, the sub-system

is sensed only within the first scan cycle. If the

applied sub-system address is changed while the

command key is pressed, the transmitted sub-sys-

tem address is not altered.

In a multiple key stroke sequence (see Figure 5)

the command code is always altered in accordance

with the sensed key.

MULTIPLE KEY-STROKE PROTECTION

The keyboard is protected against multiple key-

strokes. If more than one key is pressed at the

same time, the circuit will not generatea new output

at REMO (see Figure 5). In case of a multiple

key-stroke, the scan repetition rate is increased to

detect the release of a key as soon as possible.

There are two restrictions caused by the special

structure of the keyboard matrix :

- The keys switching to ground (code numbers 7,

15, 23, 31, 39, 47, 55 and 63) and the keys

connectedto SEN5N and SEN6N are not covered

completely by the multiple key protection. If one

sense input is switched to ground, further keys on

the same sense line are ignored, i.e. the com-

mand code corresponding to ”key to ground” is

transmitted.

- SEN5N and SEN6N are not protected against

multiple keystroke on the same driver line, be-

cause this condition has been used for the defi-

nition of additional codes (code number 56 to 63).

OUTPUT SEQUENCE (data format)

The output operation will start when the selected

code is found. A burst of pulses, including the

latched address and command codes,is generated

at the output REMO as long as a key is pressed.

The format of the output pulse train is given in

Figures 2 and 3. The operation is terminated by

releasing the key or if more than one key is pressed

at the same time. Once a sequence is started, the

transmitted data words will always be completed

after the key is released.

The toggle bits T0 and T1 are incremented if the

key is released for a minimum time tREL (see Fig-

ure 4). The toggle bits remain unchanged within a

multiple key-stroke sequence.

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