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M3005LD Datasheet(PDF) 3 Page - STMicroelectronics |
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M3005LD Datasheet(HTML) 3 Page - STMicroelectronics |
3 / 10 page 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. M3005LAB1 - M3005LD 3/10 |
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