UM3750

UN13750 Programmable Encoder/Decoder Single chip contains both Encoder and Decoder. 3V to 11 V operation. On chip oscillator uses non-critical RC components. Cross interference of recetver i s virtually eliminated by circuitry which requires 4 valid words to be received, each within 64ms of the other. Schmitt Trigger input provides excellent noise immunity. Applications. alarm control system, security system cordless telephone, remote control. Interfaces with RF, ultrasonic, or infrared modulators I and demodulators General Description T h e U M 3 7 5 0 E n c o d e r / D e c o d e r is a CMOS/LSI digital code Transmitter-Receiver system. Working in the transmit (encoder) mode, the UM3750 will sequentially encode and transmit 12 bits of input. Each of the 12 bits may be 1 or 0 to allow 4096 different codes. In the r eceive (decoder) m ode, the incoming signal is Once IS compared to the local code In a s equential manner an error comparison on the next word. If all 12 bits are received correctly, a “valid” signal is generated. This signal clears a 64ms counter and triggers a 3-stage counter. The 3-stage counter counts the “valid” pluses and when 4 pulses have been detected, the TX/RX output pin goes low. After the TX/RX output pin goes low, the next “valid” must be received within 1 28ms, giving a one valid in 6 requirement to keep the TX/RX output pin. d etected the system will r eset and beain its Pin Configurations “cc “cc TX/RX OUTPUT RECEIVER INPUT MODE SELECT “ss R.C INPUT A12 All A10 TX/RX OUTPUT RECEIVER INPUT MODE SELECT “SS R.C. I NPUT A12 All A10 NC 2-3 urn3750 Block Diagram R.C.INPUT - - - - - - - CPCLK RID I I ERROR WD TIM0 7 i VLD MXCLKR L COMPARATOR MXD Al-Al2 64ms/128ms TIMER STATE CONTROLLER CLR INIT I VALID 4 COUNTER T/R OUT Block Diagram Description CLK of Comparator CPCLK WXCLKR: CLK of Multiplexer when in Receiver mode WXCLKT CLK of Multiplexer when in Transmitter mode Output data of Multiplexer (one of Al, A2 . ... MXD: RID VLD. A12) Sampled data by Sampling CKT “Valid” signal. It is used to trigger Valid 4 Counter and reset 64ms/128ms Timer Clear signal of Comparator CLR: Error signal from Comparator ERROR: TIMER time-out signal (64ms or 128ms) TIMO : T/R OUT: Transmit/Receiver output pin Reset signal of Valid 4 Counter INIT: Word detected signal WD: Transmitter output TXO: Receiver output PXO: 2-4 UM3750 Absolute Maximum Ratings* Power Operating Supply Voltage *Comments -0 3v to 11v C Stresses Ratings” These are may a bove those ilsted Iunder cause permanent only. stress ratings “Absolute to Maximum dewce. of Temperature - 2 0 Deg to 70 D e g damage the Functional operation Storage Temperature (Tstg) Applied Voltage on any Pin --55 Deg to 150 Deg C this device at these or any other conditions above those indtcated i n the operational sections of this specification a n d e x p o s u r e t o a b s o l u t e maximuln rating m a y a f f e c t d e v i c e rellIS n ot implled vss PO.3 < v,, < v,, + o 3 c o n d i t i o n s f o r e x t e n d e d pertods ability. D.C. Electrical Characteristics (T, = 25°C. vDD = 9V ilnless o therwise specified) Input Level Input Resistor to Vcc _ 200K _ 1.2M R Oscillator F requency F _ 100 _ KHz kl5% e xclusive of external components Pin Designation Pin No. l-12 Designation Al - Al2 Description These data select lines a re used to set the addresses of the encoder/decoder pair T hey have on-chip p ull-up resistors. o s c i l l a t o r . A reslstor IS h o o k e d f r o m this pin to GND f r o m this 13 R.C. INPUT R.C. 2lRC. i n p u t pin f or sinqle pin pin t o Vcc a n d a capacttor The frequency = 14 15 Vss MODE SELECT The ground pin o f the UM3750. Receive m o d e TO T r a n s m i t mode, By This pin changes t he IC f r o m g r o u n d i n g this pin the IC IS p u t I n t o t h e R e c e i v e m o d e . B y c o n n e c t i n g to VC- t he IC IS put into the Transmit 16 RECEIVER INPUT 17 TXIRX OUTPUT mode T h e r e c e i v e r i n p u t r e c e i v e s t h e d i g i t a l P C M w a v e f o r m from t he detect CIrClllt. In the transmit m ode, this o utput pin transmlttlnq. produces the PCM waveform for I n t h e r e c e i v e m o d e , this o utput pin p r o v i d e s t h e come partson r esult and detects low If c omparison is ok. 18 Vcc The positive power s upply pin of the UM3750. 2-5 B tE z F _____ tiz = =-~ -_ _ _- UM3750 Connection Diagram for Transmitter/Receiver Output Waveform (based on 100 KHz) Typical 2-6 Decoder Flowchart Stand by M o d e Reset Count Yes + No No Data In? NO Count - C ount +1 R eset 64m s, 128ms, T imer Yes ? _!:_I- is 64ms Timer Overflow No Activates the TX//RX O u t p u t No Yes V TX,‘RX Output Ordering Information I Part No. Package 1 2-7