Glossary

active window

 
The window in flowHDL or blockHDL that the user is currently working with.  The active window will have a highlighted title bar and it will always appear to be in front of all other windows.

alias

 
A symbolic name for an expression.

arbiter

 
A device that evaluates pending requests from agents for access to a common resource and grants this resource to a master based on a specific algorithm.

arrow

 
See transition arc

asynchronous register

 
A hardware construct which combines the properties of a latch and a register.  During states in which active assignments take place, the signal behaves asynchronously.  In other states, the last value if signal is held by a register.

behavioral model

 
A simulation model described in highly abstract terms and bearing no implementation details.

bi-directional

 
a signal that can be both read and written to.

bi-directional bus

 
A collection of read/write signals that can be driven by multiple state machines.  The signal must be of MVL type and  presently, the global "z" is assigned "1" or "0," and a contention yields "x."

BIST

 
A built-in self test.

block

 
a graphical construct which represents structural components of a system.

blockdiagram

 
a diagram, composed of interconnected blocks, which represents the structure of a digital system.

buffer

 
A built-ina write signal that can be read by the source block.

bus

 
A string of text in a flowdiagram which represents a collection of signals in a digital system.

bus bit

 
A single signal of a bus.

bus slice

 
Two or more consecutive signals of a bus.

canvas

 
The area in flowHDL used to create, edit, and display flowdiagrams.

case

 
A flowdiagram object which represents a multi-way decision in the control flow of a digital system based on the value of a selected input, internal, or internal output bus.

click

 
a command directing the user to press the left mouse button.

clock

 
A signal defined for the purpose of synchronizing the actions of a system component, so that the behavior is reliable, repeatable, and stable.  Clocks controling the data path vs. the control path of a design thread are represented separately in flowHDL.

concurrent actions

 
Actions that may occur in parallel at the same instance of time.  Concurrent threads operate independently from each other.

condition

 
A flowdiagram symbol which represents a Boolean decision in the control flow of a digital system.

conditional output

 
A flowdiagram symbol which represents the placement of actions in a digital system, where activation is dependent on both the present state and specified input signals.

constant

 
A symbolic name for a hard-coded numerical value.

control path

 
The portion of a design thread, primarially represented by graphical objects and transitions, which describes the sequencing of a design’s actions.

copy buffer

 
A temporary file that contains the most recent text, object, or group of objects that were cut or copied within the current workspace. Neither flowHDL nor blockHDL will not retain the copy buffer when you move from one flowHDL or blockHDL file to another.

data path

 
The portion of a design thread, primarially represented by expressions, which describes its actions.

deadlock

 
A condition where two separate threads acquire a target resource simultaneously, but the action to be taken by each thread is blocked by the other.

dialog box

 
A window in flowHDL or blockHDL that can be used to communicate with the application through text entry and option selection.

double click

 
press the left mouse button twice quickly.

downstream design steps

 
Steps in the design process that take place after the use of flowHDL or blockHDL.

drag

 
Place the mouse pointer so that it touches an object and hold down the left mouse button while moving the mouse.  (Release the left mouse button when you have reached the desired location.)

drawing area

 
The area of the canvas used to create, edit, and display blockdiagrams or flowdiagrams.

element

 
A property of a bus representing an abstract hardware construct.

event

 
Datapath reset and control path reset events.

expression

 
The data types, operators, and macro functions associated with a flowdiagram object.

flowdiagram

 
flowHDL's graphical representation of a digital design, based from the standpoint of a time-based sequencing of control and data path actions that specify the behavior of a digital circuit.  Based on ASM chart.

flush

 
Returning a control thread to the initial state when an exception is encountered.

function key

 
A  button on a computer keyboard (labeled f1, f2, f3, etc.), usually located along the top or in a group at the right of the keyboard, that activates some function when pressed alone or in conjunction with other keys.

gated clock

 
A gated expression including a specific clock which is connected to and triggers the clock input of either a data or control path register.

gated reset/preset

 
A gated expression which includes a specific clock which is connected to and actibates the common reset or preset of a data or control path register.

ghost image

 
(a.k.a. marquee)  an image that appears on the screen when you drag an object from one location to another.  The ghost image is usually the same shape and color as the object, but contains no associated text.

group

 
the introduction of a parent block for one or more blocks.

highlight

 
An action performed by the user to set a portion of text, an object or a group of objects apart from the other text and objects in the drawing area or dialog box.

“hot key”

 
see mnemonic

input

 
a read only signal.

input bus

 
A collection of read only external signals entering the system.

input connector

 
A sub-lowdiagram symbol that represents a connection to one or more source objects located in the main flowdiagram that specifies how a subflowdiagram segment is entered.

input label

 
A flowdiagram object which is the target of an output label, showing continuity of a visually disconnected transition arc.

instantiate

 
create an instance of  a parsed-in design component in blockHDL

internal bus

 
A collection of read/write signals within the system, where all threads can read the signals but only one thread can write the signals.

internal output bus

 
A collection of output signals that can be read by all threads in the system and are also a system output.

junction box

 
a block diagram symbol which allows you to specify the routing of individual bits of a net.

latch

 
A sequential device that changes its output, at any time, in response to input changes.

latency

 
The stretch of time between the start of an operation and its completion.

live lock

 
A condition where a process loop infinitely waits for a signal which never becomes true, causing the system to become congested (a.k.a. indefinite ping-pong, starvation).

mnemonic

 

lock

 
A master’s ability to exclusively own a resource (during a set time interval) and lock out any competing agent from access.

macro-function

 
A behavioral implementation of a standard RTL function.

marker

 
a square symbol appearing at the left of an item in a pulldown menu indicating that that item is currently activated.

marquee

 
see ghost image

menu

 
A list of topics visible across the top of flowHDL’s and blockHDL's main window.  Clicking on one of these topics provides a list of sub-menu items.that can be activated by clicking on them.

metastability

 
The state of a bi-stable device when the input transitions violate setup and hold time restrictions occurring during a narrow timing window.  The bi-stable flip-flop can enter a balanced transitory state called “meta-stable.”

mneumonic

 
an underlined letter within a menu that can be used to activate that menu item through the keyboard, i.e., a “hot key”.

mode

 
A property of a signal that indicates its direction in the data path.

model thread

 
A thread in a flowHDL design designated as an integral portion of the model.  Each design must have at least one model thread.

mouse pointer

 
a small object on the screen which follows the movement of the mouse and indicates its current position.  The mouse pointer appears as an arrow by default.

net

 
a line specifying the signal paths between ports of different blocks in the block diagram and between ports and pins that cross levels in the block herarchy.

object

 
Any flowdiagram or blockdiagram symbol which appears graphically within flowHDL or blockHDL.

output

 
a write only signal.

output bus

 
A collection of write only signals that leave the system.  Each thread can have an independent output bus, but other threads cannot read that output.

output connector

 
A sub-flowdiagram symbol that represents a connection to a target object located in the main flowdiagram and specifies a sub-flowdiagram exit point.

output label

 
A flowdiagram object which is the source of an output label, showing continuity of a visually disconnected transition arc.

overwrite

 
To copy new information over existing information, erasing the existing information.

palette

 
The vertical column of buttons to the left of the drawing area that is used to place objects on the drawing area.

parse

 
extract port information from an HDL description.

pin

 
a stylized arrow directed into the block, out of the block, or in both directions which connects blocks in one level of the hierarchy to blocks at a higher level.

pipelining

 
Partitioning hardware storage into parallel blocks of registers so that multiple algorithmic solution steps can be performed at the same time.

port

 
a stylized arrow directed into the block, out of the block, or in both directions which connects blocks within one level of the hierarchy.

pull-down menu

 
a sub-menu, accessed by clicking on a main menu item, containing a list of  flowHDL or blockHDL functions that can be activated by clicking on them.

query window

 
a window in blockHDL that can be used to view underlying rules within blockHDL.  The user cannot interact with the application through this window.

radio button

 
a small character next to a string of text in a dialog box that is used to activate or deactivate an option by clicking on it.  The button appears darkened or "depressed" when activated, lightened or "undepressed" when deactivated.

register

 
See synchronous register or asynchronous register

register transfer level (RTL) model

 
A simulation model, described with basic procedural constructs and functional operators, which may be targeted for an automated synthesis tool.

reset

 
A signal or expression that resets all registers in a thread and initiates that thread.  This term is also used for a signal attached to the initial state in the control flow of a thread.

reuse

 
The ability to recall and use a resource entity (a.k.a., library lookup).

scroll

 
to view hidden text or graphics in a window through use of the scroll bar.

scroll bar

 
a graphical feature appearing along the right or the bottom of a window used to view hidden text or graphics in that window.  A scroll bar automatically appears when the text or graphical entry area in the window increases in size beyond the boundaries of the window.

semaphore

 
A flag used as an aide in locking a resource.

sheet

 
A logical partition of a flowdiagram, equivalent to a sheet of paper.

simulation

 
The act of applying input to a system to gain output response.

An object in flowHDL or blockHDL that is connected to another o

source object

 
bject (target object) through use of a transition arc.

state

 
A flowdiagram object representing a state of a digital system.

state block

 
The portion of a flowdiagram which occurs within one clock cycle, represented by a state and all objects and transitions that occur after that state and before the next state.

status line

 
 A bar located in a flowHDL or blockHDL drawing area that displays information about the currently active mode and options available within that mode, or a currently selected object.

structural model

 
A netlist representation of a device that consists of instantiated components and their interconnections.

stub thread

 
 A flowdiagram thread that is not an integral part of the design model.  Stub threads in a design may be translated separately from the rest of the model.

sub-flowdiagram

 
A special case of a sheet which is subordinate to a normal sheet and can be instantiated in multiple parts of a flowdiagram thread.

synchronization

 
A timing constraint on concurrent actions, causing some theads to wait until the current thread is finished when shared data is written to by a single thread at a time.

synchronous register

 
A sequential element which samples its input upon receiving an active control path clock edge to reflect the input to the output after a specified delay.

target  object

 
An object in flowHDL or blockHDL to which another object (source object) is connected through use of a transition arc.

terminate

 
to end the flowHDL or blockHDL application.

test harness

 
A thread containing signals used to test the design.  The test harness may be translated separately from the rest of the design, and used as simulation input.

text entry box

 
a box that, when selected by clicking on it, allows you to enter a string of text.

thread

 
A statically ordered sequence of states which may act concurrently with other flowdiagram threads in the same flowHDL file.

title bar

 
a bar located at the top of a window that displays the title of that window.

toggle

 
An item that has only two options, usually "on" and "off."

transition arc

 
A flowdiagram object, represented as a line with an arrowhead, which traces the control flow from one object to another.

type

 
The property of a signal that denotes its data values (e.g., binary, enumerated).

ungroup

 
the replacement of a selected block by its child blocks.

unit zoom

 
To increase or decrease the size of the unit used as a scale in the wave viewer.

window

 
a self-contained area within an application that contains inter-related information.

wire

 
A signal which has values assigned asynchronously and which is assigned its default value if a value is not explicitly assigned by the user.

zoom

 
To increase or decrease the magnification of graphical objects within a window.