Time-Code Reception Time-Code Reception Table of Contents General Information . 5 Introduction . 5 Time-Code Transmitters . 5 Time-Code Signals and their Reception. 6 Time-Code Receivers . 7 TEMIC Devices for Time-Code Reception. 8 U4223B . 8 U4226B . 10 T4225B . 10 INCOR - the TEMIC Software. 11 Microcontrollers . 11 M43C505 . 11 M44C588 . 11 Design of a Time-Code Receiver with U422xB. 14 U4223B Circuit Technology. 14 Board Layout . 16 Antenna Circuit . 16 Application . 16 Decoding Algorithm . 17 The Use of the TCO Signal . 18 Layout Example . 19 Data Sheets . 21 U4223B: Time-Code Receiver with A/D Converter. 21 U4224B: Time-Code Receiver with Digitized Serial Output. 39 U4226B: Time-Code Receiver with TC Output. 55 T4225B: Low-Cost Time-Code Receiver. 71 M43C505 Low-Current 3- and 5-V Solution for Consumer Applications. 87 M44C588 Versatile High-End Controller for General Purposes. 89 TELEFUNKEN Semiconductors 3 07.97 General Information Introduction Time-Code Transmitters From time to time, time deviations or power fails occur For precise time synchronization, there are four trans- to clocks and watches which must be corrected. For cor- mitters worldwide. One transmitter is located in the USA, rect time setting, an atomic clock can be used as a its reception area is more or less the entire area of North reference clock. Several transmission stations situated America. Another transmitter, located near London, worldwide send coded signals based on the atomic refer- covers UK, and a transmitter in Germany is delivering the ence clock with information on the precise time via long time information for Europe. Additionally, there is one waves. To receive and decode these signals, a special transmitter in Japan. receiver is necessary. Amplitude-modulated time-code transmitters deliver the The most convenient and exact method of time data to decode the present time (based on an atomic time synchronization for the customer is the receiver being in- normal), the day, the month and the year. They provide tegrated into the watch, automatically monitoring the also information about summer- and winter time if rele- time. An essential requirement for such a time-code vant. The information is transmitted via a long-wave receiver is a small design and low current consumption at transmitter in the frequency range of 40 to 80 kHz. This minimum voltage supply. frequency range is the best solution to construct receivers with low power consumption and high sensitivity. TEMIC was one of the industry’s first suppliers of time- code receivers and manufactured as soon as 1986 receiver circuits for general time-code applications in high- volume production. Time-code transmitter Present time Day Atomic-based time Month Year Daylight saving hour Long-wave transmitter Figure 1. Time-code transmission Table 1. The most important time-code transmitters worldwide Type Location Frequency Power Modulation ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁDCF77 Mainflingen/ 77.5 kHz 50 kW Carrier reduced by 12 dB for 100 or 200 ms ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á Frankf. a.M. (FRG) ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁJG2AS Sanwa (J) 40 kHz 10 kW Carrier switched off for 200, 500 or 800 ms ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁMSF Teddington (GB) 60 kHz 50 kW Carrier switched off for 10, 200 or 300 ms ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ÁÁÁÁWWVB Fort Collins (USA) 60 kHz 50 kW Carrier reduced by 10 dB for 200, 500 or ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ Á Á Á Á Á (unconfirmed) 800 ms ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ TELEFUNKEN Semiconductors 5 07.97 Time-Code Signals and their of a deletion takes seconds or a fraction of a second, in long waves, this can take several minutes up to half an Reception hour. Time-code transmitters on long waves are best suited for A well-constructed radio-controlled clock with a ferrite clocks with radio-controlled synchronization because antenna has high sensitivity and can pick up signals of they have good propagation characteristics and their up to some 30 dBmV/m. By using the U4223B with ADU, receivers can be dimensioned with low power consump- values of about 20 dBmV/m can be achieved. Even wrist tion. The four most important transmitters worldwide watches with their complex antenna construction (with regard to commercial clocks) are summarized in can be designed so to operate at up to approximately table 1. 40 dBmV/m. In low-cost products only 50 dBmV/m were measured. Therefore, radio-controlled clocks which Figure 2 shows the propagation distances of DCF77, receive the DCF77 signal can operate without any figure 3 the information distributed by the transmitter. problems in Germany up to a distance of 600 km from the The field strength measured in the reception area consists transmitter’s location (Mainflingen/ Frankfurt am Main). of two components: the ground wave and the space wave Within this area, the field strength is more than 1 mV/m which arises from reflections in the ionosphere. The most which is sufficient enough to guarantee good reception. predominant reception possibility exists up to a distance At a distance of more than 600 km and less than 2000 km of 2000 km from the transmitter. from the transmitter (see figure 4), radio-controlled From figure 2, it can be seen that the ground wave is still clocks can only operate with several restrictions because dominant up to a distance of almost 600 km from the ground waves and space waves become entangled. This transmitter and the field strength is at least 60 dBmV/m may cause interferences and therefore deletion of the (1 mV/m). Ground waves and space waves become signal. Radio-controlled reception is nevertheless pos- entangled at distances between 600 and 2000 km. Recep- sible in this area by using highly efficient antennas and tion is then less stable due to interferences. In long receivers as well as intelligent decoding software. Best distances, longest stable field strengths can be expected reception time is the night time as a lot of interference at night time. While in short waves, the transmission time sources are then switched off. 110 100 90 Ground wave 80 m 70 Night 60 50 Winter day Space waves Field strentgh ( dB V ) V Field strentgh ( dB 40 30 Summer day 20 10 0 100 1000 10000 13323 Distance ( km ) Figure 2. Propagation distances of the time-code transmitter DCF77 6 TELEFUNKEN Semiconductors 07.97 Time frame 1 minute Time frame ( index count 1 second ) 0 5 10 15 20 25 30 3540 45 50 55 0 5 10 Coding Minutes Hours Calendar Day Month Year when day of required the week Example: 19.35 h s 1 24810 20 40 P1 1 2 4 81020P2 Sec. 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Minutes Hours Start bit Parity bit P1 Parity bit P2 93 7527 e Figure 3. The German transmitter DCF77: a typical time-code example 2000 km 600 km Figure 4. The propagation area of the time-code transmitter DCF77 Time-Code Receivers The first approach is a straight-through receiver which obtains the signal from a ferrite antenna (tuned to the desired frequency) and amplifies it. The selectivity is Radio-controlled clocks receive time-code signals from achieved by using one or two crystal filters. The AM regional time-code transmitters around the world in the modulation is toggling the decoder stage. At the output of VLF area. The signal is received and decoded by the the decoder stage (TCO), a rectangular signal, following radio-controlled system. the amplitude modulation, is present. The second solution is using the U4223B which delivers TEMIC offers two different solutions to receive time- a 4-bit digitized signal to the microcontroller. By means code transmissions. Both solutions have the same of TEMIC’s software INCOR , an improved overall sensi- receiving concept. tivity of more than 6 dB can be achieved. TELEFUNKEN Semiconductors 7 07.97 TEMIC Devices for Time-Code Reception U4223B summer- to winter time is also carried out in each individual country if the information from the transmitter TEMIC launched a new era in precise and user-friendly is available. radio-controlled clocks when the first TEMIC ICs for The U4223B family offers high sensitivity and low power radio-controlled consumer clocks were introduced in consumption. The circuit can be used for universal appli- 1986 and has remained a leader in this field since then. cations due to its supply voltage of 1.2 V to 5.25 V. With µ µ The U4223B family was developed to achieve constant its typical power consumption of 13 A to 20 A, it is high sensitivity rates with low voltage and power con- particularly suitable for long-life battery applications. sumption. Therefore, radio-controlled clocks as well as Features all other clocks and wrist watches can be used with D standard batteries and have very long operating times. Very low power consumption D m Radio-controlled clocks consist of an antenna, a receiver Very high sensitivity (1 V typical) circuit, a microcontroller as well as various display and D Choice of selectivity by use of one or two input elements. The U4223B is a very efficient receiver crystal filters circuit which can be universally applied for receiving the D time-code signals in the VLF area. Furthermore, the Power-down mode available TEMIC MARC4 microcontroller family can be used in D Few external components necessary applications with the U4223B and U4226B for radio- D controlled systems. 4-bit parallel output D AGC hold mode for bridging over known inter- The radio-controlled clock is constantly set precisely. ferences (e.g., stepper motor) Therefore, the internal crystal clock is then set precisely to the second by the received signal.