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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 Table 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 6). The format of the

output data is given in Figure 5 and 6. The data

word starts with two toggle bits T1 and T0, fol-

lowed by three bits for defining the sub-system ad-

dress S2, S1 and S0, and six bits F, E, D, C, Band

A which are defined by the selected key.

In the modulated transmission mode the first tog-

gle 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 instruc-

tion has to be considered as a new command. The

codes for the sub-system address and the select-

ed key are given in Table 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 res-

onator.

FUNCTIONAL DESCRIPTION

Keyboard operation

In the stand-by mode all drivers (DRV0N to

ever a key is pressed, one or more of the sense in-

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

power-up sequence. First the oscillator is activat-

the output drivers (DRV0N to DRV6N) become ac-

tive 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 in-

ternal data latch.

In contrast to the command code, the sub-system

is sensed only within the first scan cycle. If the ap-

plied 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 8)

the command code is always altered in accor-

dance 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 generate a new out-

put at REMO (see Figure 8). 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 command code corresponding

to ”key to ground” is transmitted.

– SEN5N and SEN6N are not protected against

multiple keystroke on the same driver line,

because this condition has been used for the

definition 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 generat-

ed at the output REMO as long as a key is

pressed.

The format of the output pulse train is given in Fig-

ure 5 and 6. The operation is terminated by releas-

ing 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

ure 7). The toggle bits remain unchanged within a

multiple key-stroke sequence.