STV3012 查看數據表（PDF） - STMicroelectronics

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STV3012

REMOTE CONTROL TRANSMITTER FOR AUDIO AND VIDEO APPLICATIONS

STMicroelectronics 

STV3012

I.4 - Oscillator Input and Output

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. No external feedback resistor is allowed.

II - FUNCTIONAL DESCRIPTION

Key operation (see Figure 3) :

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 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 the command

code is always altered in accordance with the

sensed key.

III - 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 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 T1 and T0, during mode A only T0,

toggle if the key is released for a minimum time

tREL. The toggle bits remain unchanged within a

multiple key-stroke sequence.

IV - MULTIPLE KEY-STROKE PROTECTION

The keyboard is protected against multiple key-

strokes (Figure 4). If more than one key is pressed

at the same time, the circuit will not generate a new

output at REMO. 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 switch-

ing to ground (code numbers 7, 15, 23, 31, 39, 47,

55 and 63) and the keys connected to 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).

Figure 3 : Single Key-stroke Sequence. Debounce time : tDB = 4 to 9 x t0,

Start time : tST = 5 to 10 x t0, Minimum release time : tREL = t0.

REV closed

released

key bouncing

scan

DRVnN off

on

t DB

H

REMO

L

tW

t ST

scan

t REL

new key

scan

new word

H

OSCO

L

OSCILLATOR ACTIVE

6/8

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