155 decoder logicworks code#

Some other encoder ICs also feature extra inputs and outputs that allow several ICs to be connected together to achieve more flexibility in the numbers of input and output lines available.

The input pins may be used to connect to switches on a decimal keypad, and the encoder would output a 4-bit BCD code, (0000 2 to 1001 2) depending on which key has been pressed, or simply to identify which one of ten input lines in a circuit is active, by outputting an appropriate number in four bit BCD code. The tenth condition (zero) is assumed to be present because when none of the 1 to 9 input pins is active, this must indicate zero. For example, a simple decimal to BCD (or 10-to-4 line) encoder would be expected to have ten input pins, but in fact the 74HC147 has only 9. 4.4.1 74HC147 10-to-4-Line Priority Encoderĭepending on the encoding purpose, each each different IC has its own particular method for solving encoding problems. The Pinout diagram for the 74HC147 10-to-4-line priority encoder from NXP (Philips Semiconductor), is illustrated in Fig.4.4.1.įig. For example, if 6 and 7 are pressed together the BCD output will indicate 7.

155 decoder logicworks code#

The encoder then produces a binary code on the output pins, which changes in response to the input that has been activated.īecause it is always possible when using input switches that more than one input may be active at a single time, most encoders of this type feature ‘priority encoding’ where, if more than one input is made active at the same time, the output will select only the most significant active input. only one of the inputs can be active at any one time. Priority Encodersīinary Encoders generally have a number of inputs that must be mutually exclusive, i.e. Notice that the word ‘code’ appears in each of these titles, and a binary code differs from normal binary because it is arranged in a particular way to suit a given purpose. Decimal numbers in a calculator may be sent to a numeric display using BCD (Binary Coded Decimal). For example text may be represented by an ASCII code (American standard Code for Information Interchange), in which each letter, number or symbol is represented by a 7-bit binary code.

Mathematics, graphics, data manipulation and physical control systems are among many of the functions that are carried out using binary data, and each of these uses may require binary data arranged in various forms of binary codes.

Simulate circuit operation using software.ĭigital Electronics Module 1 (Number Systems) described a number of different binary codes that are used to perform a range of functions in digital circuits.

Understand common features on Decoders/Demultiplexers.

Understand the operation of Decoders/Demultiplexers.

Understand the operation of Binary Encoders.

Recognise the need for Code Converters.

After studying this section, you should be able to:.

Label your selectors as S0,S1,S2,S3 with S0 as the least significant bit. Whichever parts you choose to construct your circuit, your design should select one of the 16 data input lines to be the final output. You will need three 74_153 muxes with the outputs from two of them serving as inputs to the A0-A3 pins of a third 74_153 mux ( B0-B3 and YB won't be used in the third one). The selector inputs S1 and S0 select one line from A0-A3 as output YA and one line from B0-B3 as output YB. Set the GA (enable) and GB (ground) pins to 0. In LogicWorks they are in the 7400DEVS.CLF library under the name 74_153. These are actual TTL (Transistor-Transistor Logic) chips you could buy at Radio Shack or online. Another way to construct the MUX is using 7400-153 dual 4-to-1 line multiplexers. Hint: For the 4-to-1 line multiplexer you only need to use one of the selector inputs and two of the data inputs. Set the Enable ( EN) pin for each mux to 0. You can find these parts in LogicWorks in the Simulation Logic.clf library. Construct the MUX out of two 8-to-1 line multiplexers (Mux-8) and a 4-to-1 line multiplexer (Mux-4). Use LogicWorks to construct a simulation of a 16 x 1 multiplexer. Remember that LogicWorks uses negative-logic decoders, so you enable decoders with a value of zero on the EN pin. Use A3and A4 for the selectors for the 2x4 decoder. Use the first three inputs as the selector values for the 3x8 decoders.

Label your inputs A0,A1,A2,A3,A4 where A0 is the least significant input digit. Use the 2x4 decoder to select which of the 3x8 decoders is enabled. Build your decoder with one 2x4 decoder and four 3x8 decoders (found in the Simulation Logic.clf library). Use LogicWorks to construct a simulation of a 5x32 decoder.