Logic

Features

• AND, NAND, OR, XOR, and NOR Gates
• Buffer and Inverter Gates
• 2-Input Schmitt Trigger Gates
• Type, Quad-D, and J/ K* Flip-Flops
• Set/Reset Latch, 8-bit Transparent Latch
• Shift Registers, Counters
• PROM
• Digital Phase/Frequency Detector
• Digital Multiplexers, Demultiplexers
• Analog Multiplexers, Demultiplexers
• One-shot (Retriggerable Monostable Multivibrator)
• Digital Comparator
• Analog Comparator

Overview

The optional SystemVue Logic Library has three classifications of tokens:
Generic Tokens include well-known functions such as the NAND gate. These generic logic tokens can have an unlimited numbers of inputs. For example, you may use the NAND token to create a 2-input NAND gate, a 5-input NAND gate, etc.

7400 Tokens simulate functions available as off-the-shelf parts. In SystemVue, “74xx” refers to a specific logic function and not to a family such as TTL or CMOS.

Custom Tokens implement logic functions not generally available as off-the-shelf parts, or mixed-signal functions such as an analog switch, analog comparator, 16-bit DAC, or 16-bit ADC. Logic parameters can be independently set on each device, including logic thresholds, the amplitude and polarity of the HIGH and LOW states, and the output delay of the function. The default propagation time (output delay) is zero seconds to be consistent with the logic tokens that are in the main Operator library.

The Logic library may be used on a stand-alone basis to simulate systems such as a sequencer or digital sliding correlator, or it may be combined with the Communications, DSP, or RF/Analog libraries to enhance their capabilities. An example of this multi-library use would be the simulation of a PLL (phase-locked loop) shown below. This PLL uses the MC4044 Digital Phase/Frequency Detector and the 744040 12-stage binary counter from the Logic Library, and an Op-Amp type lowpass filter from the RF/Analog Library.

Logic and RF/Analog library models are used to create a PLL simulation.

Another application of the Logic Library is the combination of a shift register with glue-logic gates to build a pseudo- random noise generator that has custom feedback- tap locations and a specific seed value.

Design Example
The Logic Library is used in the simulation of a staircase / triangle wave generator system shown below. The binary output of an up/down counter is connected to a Digital-to-Analog Converter. The analog output of this DAC goes to two analog comparators, each with a different reference input.

A staircase/triangle waveform generator.

The outputs of the comparators connect to a set/reset latch (cross connected NAND gates). Since each comparator output is a momentary LOW going pulse, the latch provides the memory element required. The output of the latch determines the direction, up or down, of the counter.

Step Function source tokens are used to tie off the unused inputs of the logic circuits. They are also used to set the reference levels of the comparators.

A Logic Buffer token is used to route the interconnecting lines for a more pleasing appearance. Since the logic thresholds and the HIGH/LOW outputs can be set to any value, slightly staggering these values will allow overlapping plots to be easily viewed in the display window.

The triangular staircase output of the DAC and the
continuous clock input to the up/down counter.

The output of the latch. HIGH = count down, LOW = count up.

Library Tokens

Latches

• 8-Bit Transparent Latch with Q Output
• Set / Reset Latch (Two NAND gates, cross-coupled)

Shift Registers

• 8-Bit Serial-in / Parallel-out Shift Register

Counters

• 4-Bit Synchronous Binary Up/Down Counter, with One Clock
• 4-Bit Synchronous Presettable Binary Counter
• 12-Stage Binary Counter

Digital Multiplexers

• 8-Input Digital Multiplexer

Digital Decoders / Digital Demultiplexers

• 3-Line to 8-Line Decoder/Demultiplexer

Switches / Analog Multiplexers / Analog Demultiplexers

• 2-Channel Analog Multiplexer (SPDT Analog Switch)
• 2-Channel Analog Multiplexer/Demux (DPDT Analog Switch)

Arithmetic Circuits

• 8-Bit Identity Comparator (Equality Detector)

Miscellaneous

• Comparator (Differential Analog Input, Q and Q* Output)
• n-Bit Analog to Digital Converter (ADC)
• n-Bit Integer to Digital Converter
• n-Bit Digital to Analog Converter (DAC)
• Phase-Frequency Detector
• Programmable Read Only Memory, 8 x 8 (PROM)
• Retriggerable Monostable Multivibrator

Additional Resources

• Read the manual ( 907kb)

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