A New System of Digital Circuit Blocks for Industrial Measuring and Control Equipment [*1
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164 PHILlPS TECHNICAL REVIEW VOLUME26 A new system of digital circuit blocks for industrial measuring and control equipment [*1 D. Gossel, G. Kaps and W. Schott 621.374.32 Introduetion Fig. 1 shows the AND and OR operation realized with The characteristic of digital information processing NAND- and NOR-blocks. Each NAND and NOR installations is that in their construction a small group symbol represents one basic circuit containing at least of basic circuits is used, each of which occurs in large one transistor together with resistors, capacitors and numbers. The group of basic circuits is called a system. diodes. In order to enable designers to realize a given logical design without going into electronic details, several manufacturers have developed systems consisting of "And", "Or" and "Negation" circuit blocks as well as bistable circuits (flip-flops) for counting and storing purposes [11. Although it should be possible to realize any logical design using such a system, circuit limitations must be considered, and extensive load tables limit the possibil- ities of combining the various blocks. The number of prohibited combinations increases with the number of different blocks, making the load tables more and more complicated. Amplifiers for decoupling purposes - e.g. P-N-P and N-P-N emitter followers - have to be used, although they have no logical function, and this is at variance with the original aim [21. Consequently there are systems in which the total number of blocks required for a given problem bears no relation to the number that have a logic function. This influences not only costs, but .also reliability, since an increase in the number of blocks also causes an increase in the failure rate. Efforts have been made to avoid these difficulties by Q decreasing the number of basic circuits. Switching Fig. 1. Logic circuits for the OR operation and the AND opera- algebra provides a solution through the use of De tion, built up of a) NAND circuits, b) NOR circuits. Morgan's formula [31: A second advantage of using only one type of block Xl + X2 + ....+ Xn = Xl • X2 ••••• Xn, for all logical circuits is that the load tables in the NAND and NOR systems reduce to one single load xi . X2 ••••• Xn = xi + X2 + ... + xn· rule. It is only necessary to know how many NAND This formula gives the relationship between the AND or NOR circuits can be reliably controlled by a pre- and OR operation and the Negation. It may be seen vious NAND or NOR. There are no other forms of from this that the one operation can always be replaced . loading. by the other together with the negation. A serious disadvantage however is the large number The NAND and NOR techniques often used at ' of blocks to be used for certain operations. In order to present go another step further. Here it is possible by realize an OR operation, one relatively expensiveNAND using suitable combinatieris of the AND operation block is necessary for each input (fig. la). The AND t?gether with negation, or the OR operation together [*1 Editorial note: An article by E. J. van Barneveld, Philips with negation, to make only one type ofblock suffice [41. ICOMA Division, Eindhoven, will be appearing shortly in this journal, describing another system of digital circuit blocks, Dipt-Ing. D. Gossel, iJipl.-Ing. G. Kaps and Dipt-Ing. W. Schoft designed for more universal use than the system presented are research workers at the Hamburg laboratory of Philips here, and which is now being put into production by the Zentra/laboratorium GmbH. ICOMA Division. ' {) 1965, No. 4/5/6 SySTEM or DIGITAL ClRCUlT BLOCKS 165 operation, however, can always be realized by two maximum load per stage is much reduced in asynchron- NAND blocks regardless of the number of inputs ous counting techniques. (within certain limits). This also holds true when only When somewhat higher demands are made, the NOR blocks are used; but in this case AND and OR synchronous counting mode is to be preferred because operations are exchanged (fig. lb) [51. of its great advantages, although a few more blocks are needed. Here all the stages of a counting circuit The new building-block system receive switching pulses from a common clock-pulse The new system of digital circuit blocks described in generator. Each stage contains a separate signal input S, this paper. can be regarded as an attempt to reach a and the voltage applied to this input determines whether good compromise between these two methods. One of or not a given clock pulse will trigger the circuit. This the characteristics of the new system is the use of only method has the following consequences. two basic circuits, an active one, and a passive one. a) The circuit is very insensitive to interference. As a The active block contains a circuit in diode-transistor result of the delaying effect of the pulse gate con- logic (DTL). With the logic convention chosen trolled via the S input, parasitic pulses in the signal ("1" ,.....12 V, "0"""" 0 V) this block works as a NOR line will only be able to cause incorrect switching if circuit (fig. 2). The passive block is an AND circuit their duration is > 5 (Ls, and their voltage-time (also called an AND gate) with two inputs (fig. 3). integral is more than 60 (LVs, and the clock pulse The number of inputs can within wide limits be in- is received more than 5 (Lsafter the start of a para- creased by means of additional diodes. Using the sitic pulse. Under normal conditions it is unlikely passive AND block it is not necessary to realize the that these three conditions will be satisfied simul- AND operation with NOR blocks in the expensive taneously. In practice therefore there will be almost way shown in fig. lb. no interference. This building-block system which is especially b) The various stages are not subjected to a dynamic designed for industrial measurement and control pur- load of any significance, since the triggering energy poses also has the following characteristics. is supplied by the common clock-pulse generator. 1. There are no emitter followers. Only one type of With the exception of the clock-pulse line, which transistor and two types of diode are used. should be as short and of as low capacity as possible, 2. A standardized voltage supply is used (± 12 V all signal lines are uncritical. ± 5 %). This value is considered a good compromise c) Unlimited use may be made ofthe maximum switch- between ing frequency. All stages which have to be triggered a) a high voltage, giving low sensitivity to interference are prepared during the interval between two clock and great freedom in combining various numbers pulses, and are triggered by the next clock pulse and types of block - i.e. wide signal tolerances are received. The switching times of successive stages permitted -, and are not additive. No stringent demands are made b) a low voltage which suits the low maximum per- for the rise time of the signal voltage at the Sinput. missible voltage for available transistors and gives low dissipation. [1] G. Schinze, Das AEG-Steuerungssystem "Logistat", AEG- Mitt. 50, 76-83, 1960. 3. The maximum switching frequency is 80 kc/s, the W. Stübchen, Ruhende Steuerungen Logistat - die sinnvolle maximum counting frequency 30 kc/so (In some cases industrielIe Anwendung kontaktloser Steuerungen, AEG- Mitt.SO, 139-143, 1960. the maximum counting frequency may be 80 kc/s.) In Valvo-Handbuch Bausteine, Digitale Bausteine, ValvoGmbH, industrial applications the electronic circuits are mainly Hamburg 1962. Catalogue of Akkord-Radio GmbH, Herxheim/Pfalz, Esta- used together with moving parts which have a certain cord - Das universelle Bausteinsystem für kontaktlose mass. Experience here has shown that resolving power Steuerungen. Catalogue 3.62 of Ebauches S.A., Neuchätel, Switzerland, (accuracy) and speed call for a counting frequency of Transistorisierte logische Einheiten. 10 kc/s at the most. A frequency of 30 kc/s is thus A. Stopp, Normalkonstruktionen der BBC-Elektron ik, BBC- Nachr. 42, 199-207, 1960. adequate for quite extreme requirements. K. Stahl, M. Syrbe, H. Lisner and G. Hanke, Grundlagen 4. Asynchronous or synchronous modes of operation und Aufbau der BBC-Elektronik, BBC-Nachr. 42, 208-219, 1960. are optional. For simple problems involving low-speed [2] W. Händler, Digitale Universalrechenautomaten; section counting, the well-known asynchronous method may 10.1.2.1., Vollständige Systerne, in: K. Steinbuch, Taschen- buch der Nachrichtenverarbeitung, Sp;ringer, Berlin 1962. be used. Here for example a bistable circuit is triggered [3] U; Weyh, Elemente der Schaltungsalgebra, R. Oldenbourg, by a previous one which also has to supply the switch- Munich 1960. [4] Valvo-Handbuch Bausteine, Norbit Bausteine, Valvo GmbH, ing energy. The maximum counting rate is determined Hamburg 1962., _ by the sum of the switching times of all stages and thus [5] E. Rohloff, Aufbau und Anforderungen bei kontaktlosen Steuerungen für die Industrie, Elektron. Rdsch. 15, 99-102, decreases with an increasing -number of stages. The 1961. 166 PHILlPS TECHNICAL REVIEW VOLUME26 5. The circuits have been designed to allow for the most unfavourable voltages and resistances within the toler- ances quoted, and for the transistor data at the end of the operating life; undisturbed operation under full load is guaranteed in the temperature range from -10 oe to +50 oe. 6. Signal tolerances: "I" /'...+6 ... + 12 V, "0" /'... O ... + 1.8 V. Q The two types of block Fig. 3. a) Circuit ofthe AND gate, b) arrangement of the contacts. The active block (jig. 2a) contains a gate circuit with diodes (Dl ... D5, RK, RB), an inverter circuit The passive block (jig.