SUMMARY

Now that you have completed this chapter, you should have a basic understanding of the more common special logic circuits. The following is a summary of the emphasized terms and points found in the "Special Logic Circuits" chapter.

SPECIAL LOGIC CIRCUITS perform arithmetic and logic operations; input, output, store and transfer information; and provide proper timing for these operations.

EXCLUSIVE OR (X-OR) circuits produce a 1 output when ONLY one input is HIGH. Can be used as a quarter adder.

EXCLUSIVE NOR (X-NOR) circuits produce a 1 output when all inputs are 0 and when more than 1 input is 1.

QUARTER ADDER circuits produce the sum of two numbers but do not generate a carry.

HALF ADDER circuits produce the sum of two numbers and generate a carry.

FULL ADDER circuits add a carry to obtain the correct sum.

PARALLEL ADDER circuits use full adders connected in parallel to accommodate the addition of multiple-digit numbers.

STANDARD SYMBOLS depict logic circuitry with blocks, showing only inputs and outputs. One block may contain many types of gates and circuits.

SUBTRACTION in binary is accomplished by complementing and adding.

FLIP-FLOP are bistable multivibrators used for storage, timing, arithmetic operations, and transfer of information.

R-S FFs have the Q output of the FF HIGH in the set mode and LOW in the reset mode.

T (TOGGLE) FF_S change state with each pulse applied to the input. Each T FF will divide the input by 2.

D FF is used to store data at a predetermined time.

J-K FF is the most versatile FF. J-Ks can perform the same functions as all the other FFs.

CLOCKS are circuits that generate the timing and control signals for other operations.

COUNTERS are used to count operations, quantities, or periods of time. They can be used to divide frequencies, to address information in storage, or as temporary storage.

MODULUS of a counter is the total number of counts or stable states a counter may indicate.

UP COUNTERS count from 0 to a predetermined number.

DOWN COUNTERS count from a predetermined number to 0.

RING COUNTERS are loop counters that may be used for timing operations.

REGISTERS are used as temporary storage devices as well as for transfer of information.

PARALLEL REGISTERS receive or transfer all bits of data simultaneously.

SHIFT REGISTERS are used to perform serial-to-parallel and parallel-to-serial conversion and for scaling binary numbers.

SERIAL TRANSFER causes all bits of data to be transferred on a single line.

PARALLEL TRANSFER has each data bit on its own line.

SCALING of binary numbers means to increase or decrease the magnitude of a number by a power of 2.

LOGIC FAMILIES are composed of logic circuits based on particular types of elements.