What is the structure and application of programmable array logic?

The output and response structure is composed of programmable and array and fixed or array. There is no output response signal. The input and output terminals are fixed and cannot be defined by the user. Only applicable to a simple combinational logic circuit scheme.

1. Input and output structure

　　With three-state output buffer and echo buffer. The reverberation buffer can make the three-state output reverberate to the input end of the array, forming a simple trigger, so that the output has a recall function. The user can control the status of the three-state output buffer after programming, and then complete the intentional configuration of the input/output pinout. Using programmable input/output PAL equipment, it can program encoders, decoders, data selectors and other combinational logic circuits, as well as serial data shift and cycle operations.

2. Storage type structure with response

　　 has a retrospective function, because all equipment only needs a common clock and an output enable input, so it can form a counter equivalent step sequential logic circuit.

3. Storage type structure with XOR

　　 The output of the array is divided into two groups, which is added to the input of the D flip-flop after the exclusive OR operation, which makes the logic circuit scheme more active and convenient.

4. Arithmetic gate reverb type structure

　　Add an arithmetic strobe circuit on the basis of the XOR PAL, and generate the four largest terms of the input signal and the reverberation signal. The four largest items generated by the arithmetic strobe circuit are added to the input of the AND array. After programming the AND array, 16 kinds of logic combination outputs can be obtained.

　　Arithmetic gated reverb type PAL equipment is mainly used for arithmetic logic circuits such as addition, subtraction, greater than and less than the completion of the network.

5. Product term shared output structure

　　 Two adjacent logical unit product terms can be connected to two OR gates together.

6. Macro cell output structure

The macro cell of PAL22V 10 is composed of a trigger and two programmable multiplexers. After programming the two multiplexers, each macrocell can set 4 output construction methods and two kinds of response signals, so it has Stronger versatility and flexibility.

　　Use

　　PAL equipment has high speed, low power consumption, and has a variety of construction types, which can be used to program various combinational logic circuits and sequential logic circuits. When planning, the first considerations are the following:

　　 (1) The total number of input/output terminals of a PAL device is limited.

　　 (2) The number of output product terms for each PAL device is limited.

        (3) In the PAL equipment with a storage and a macro unit structure, when the storage in the logic unit is used as an internal response storage, a logic unit needs to be occupied, then the corresponding output pin cannot be used for other purposes; when the logic When the unit is used as a combined output, it also occupies a logical unit, and its internal storage cannot be used.

If you want to know more, our website has product specifications for programmable array logic, you can go to ALLICDATA ELECTRONICS LIMITED to get more information