## A. List of Built-In Gate Types

Name | Keywords(s) | Shortcut(s) | Symbol | Description
--- | --- | --- | --- | ---

AND

and, nand

a
A

Outputs the logical AND of the input signals. All of the inputs must be have either the same bit width as the output, or be single bit. In the case of a gate with mixed multi- and single-bit inputs, the single-bit inputs are assumed to be connected to across all bits of the multi-bit signals.

OR

or, nor

o
O

Outputs the logical OR of the input signals. All of the inputs must be have either the same bit width as the output, or be single bit. In the case of a gate with mixed multi- and single-bit inputs, the single-bit inputs are replicated to all of the other bits.

XOR

xor, xnor

x
X

Outputs the logical XOR of the input signals. All of the inputs must be have either the same bit width as the output, or be single bit. In the case of a gate with mixed multi- and single-bit inputs, the single-bit inputs are replicated to all of the other bits.

Buffer

buf, not

b
I

Buffers the input signal. If the input signal is a value other than logic-1 or logic-0 (e.g., floating) the output will be the unknown signal. The inputs and outputs must have the same bit width.

Tri-State Buffer

bufif1, bufif0,
notif1,notif0

t

Outputs a buffered signal when the enable line (top) is logic-1. Note that an inverter placed on the output of a tri-state buffer is not equivalent to connecting the output to a separate inverter element. With an inverted output, a logic-0 on the enable line will result in floating output (i.e., Verilog notif behavior). The input and output must have the same bit width, and the enable line must be single bit.

Reduction Gates

and, nand,
or, nor,
xor, xnor

Ctl-r a | Ctl-r A
Ctl-r o | Ctl-r O
Ctl-r x | Ctl-r X

Outputs the logical AND of all of the bits on the input. Reduction gates for OR and XOR are also available. The output must be single-bit.

Constants

supply1, supply0

g | v

Outputs a logic-1 or logic-0. There are no bit-width restrictions.

Switch

switch

s

Outputs a single-bit logic value according to the switch setting. Clicking on a switch while in simulation mode will toggle its state. The output must be single-bit.

Dip Switch

dip

d

Outputs a multi-bit signal according to the switch setting. Clicking on a dip switch while in simulation mode will enable a hex value for the switch to be entered.

Tty

tty

d

Tty gates can be used to model an interactive terminal. Your circuit can send characters to be displayed on the tty, or receive

###

characters that were typed in the tty. See the section on ttys in the simulator manual for details on how to use ttys.

Clock

clock

c

Outputs a clock signal with a specified pulse-width (f), phase (p), and duty width(dw). The output must be single bit.

Concat

concat

w

Combines multiple wires into a single multi-bit wire. The sum of the bits on the left side must add up to the bit width of the right side. The current implementation has a limitation that all signals must flow in the same direction. That is, you must put all of the driving gates on either the left or right.

Wire Tap

n/a

n/a

Pulls off a sub-range of a multi-bit wire. This gate type is not created through the menus like most other gates, but by dropping the end of a wire on a wire of a larger bit-width. You can use the "Properties..." option from the "Gate" menu to select the bit range to be extracted. This gate can only be used to "read" the value of a wire, and cannot be used to "wire" a value on a multi-bit bus.

Adder

add

+

Outputs the sum of the inputs. The inputs must have the same bit width as the output, and the carry-in and -out must be single bit. The carry-in line is indicated by the dot.

Divider

div

/

Outputs the quotient and remainder of the inputs. The left input is the dividend, and the right input is the divisor. There are no bit-width restrictions, but if the result does not fit in the supplied bit-width, it may be truncated.

Multiplier

mult

*

Outputs the product of the inputs. There are no bit-width restrictions, but if the result does not fit in the supplied bit-width, it may be truncated.

Multiplexer

mux

m

Outputs the input selected by the select line. The bit-width of the inputs must match the bit-width of the output, and the bit-width of the select line must be the ceiling of the base-2 log of the number of input lines.

Decoder

demux

D 2

Outputs the input selected by the select line. The bit-width of the inputs must match the bit-width of the output, and the bit-width of the select line must be the ceiling of the base-2 log of the number of input lines.

Left Shift

lshift

S L

Performs a logical shift-left of the input. The input and output must have the same bit width, and the bit-width of the shift select line must be the ceiling of the base-2 log of the input/output bit-width.

Right Shift

rshift

S R

Performs a logical shift-right of the input. The input and output must have the same bit width, and the bit-width of the shift select line must be the ceiling of the base-2 log of the input/output bit-width.

Arithmetic Shift

arshift

S A

Performs an arithmetic shift-right of the input. The input and output must have the same bit width, and the bit-width of the shift select line must be the ceiling of the base-2 log of the input/output bit-width.

Roll

roll

S O

Rolls the input bits to the left. The input and output must have the same bit width, and the bit-width of the shift select line must be the ceiling of the base-2 log of the input/output bit-width.

Register

register

r

Outputs the current value of the register, and stores the input value on a positive edge on the clock line. The data value is only loaded when the active-low enable (EN) line is asserted. The register can be cleared asynchronously with the active-low clear (CL) line. The input and output must have the same bit width, and the clock, EN and CL lines must be single-bit.

Flip-Flop

ff

f

Outputs the current value and inverted value of the flip-flop, and stores the input value on a positive edge on the clock line. The data value is only loaded when the active-low enable (E) line is asserted. The flip-flop can be cleared asynchronously with the active-low clear (C) line. The input and output must have the same bit width, and the clock, E and C lines must be single-bit.

RAM

ram

R

When the chip-select line (CS) and output enable (OE) lines are low, the memory value addressed by the address line (A) is output to the data line (D). When the chip select line and the write enable line (WE) are low, the value present on the data line is stored in the memory at the address specified by the address line. The control lines, CS, OE, WE must be single-bit. The address and data lines must be no more than 32 bits. RAMs can be initialized from a file at simulation time.

ROM

rom

u

When the output enable line (OE) is low, the memory value addressed by the address line (A) is output to the data line (D). The output enable line must be single bit, and the address and data lines must be no more than 32 bits. ROMs can be initialized from a file at simulation time.

NMOS Trans.

nmos

Ctl-t n

Implements a Verilog-style NMOS element. All signals must have the same bit width. NMOS elements with multi-bit inputs and outputs are treated as parallel transistors.

PMOS Trans.

pmos

Ctl-t p

Implements a Verilog-style PMOS element. All signals must have the same bit width. PMOS elements with multi-bit inputs and outputs are treated as parallel transistors.

LED

led

l | L 8
L s | L h
L d

LED Indicator elements which can display the values of signals in your circuit. The different types of LED are indicated by a property flag of the basic LED circuit element. The types from upper left are: bit, bar graph, direct, hexadecimal and decimal. The number of digits or bars is automatically determined from the size of the input wire. For the three types of 7-segment LEDs, the interpretation of the input data depends on the type. For direct LEDs, each 7-bits of the input signal directly control one segment of the LED numbered from top-to-bottom, left-to-right. For hexadecimal LEDs, each four bit group controls one digit. For decimal LEDs, the value of the input signal is displayed as an unsigned decimal value.

Module

name

M

Implements a user-defined module. An arbitrary number of inputs, outputs and inout ports can be used with no restrictions on bit width. The name of the module is used in the save file and cannot be the same as any of the built-in gates.

Comment

comment

C

Comments can be used to place embed text into a circuit diagram. Comments have no effect on the behavior of circuits.

Frame

frame

F

Frames can be used to create visual segmentation of a circuit diagram. Frames have no effect on the behavior of circuits.