hades.models.rtlib.memory
Class RAM

java.lang.Object
  hades.simulator.SimObject
      hades.models.rtlib.memory.GenericMemory
          hades.models.rtlib.memory.RAM

All Implemented Interfaces:

java.lang.Cloneable, ContextToolTip, Memory, java.io.Serializable, Simulatable

Direct Known Subclasses:

i4004InternalReg

public class RAM

extends GenericMemory

RAM - a generic RAM with n words by m bits with asynchronous (level sensitive) write enable and separate active-low chip select. When chip-select is high, the data output of the RAM is tristated and writes are ignored. This component models a standard MSI/LSI RAM with asynchronous write enable - the adress is never latched. As long as write enable is low, the input data is written to the currently selected address.

Note that the model currently does not check for timing violations during write cycles.

See Also:

Serialized Form

Field Summary

protected PortStdLogicVector	port_A
protected PortStdLogicVector	port_DIN
protected PortStdLogicVector	port_DOUT
protected PortStdLogic1164	port_nCS
protected PortStdLogic1164	port_nWE
static double	t_access
static double	t_min_we_cycle
static double	t_setup
static double	t_tristate
static double	t_undefined

Fields inherited from class hades.models.rtlib.memory.GenericMemory

bit_mask, data, enableAnimationFlag, last_read_addr, last_read_data, last_write_addr, last_write_data, MEF, n_bits, n_words, resourcename, TRISTATED, UNDEFINED, vector_000, vector_111, vector_UUU, vector_XXX, vector_ZZZ

Fields inherited from class hades.simulator.SimObject

classloader, console, debug, editor, name, parent, ports, propertySheet, simulator, symbol, versionId, visible

Constructor Summary

RAM()
RAM constructor

Method Summary

boolean	canChangeSize()
protected void	constructPorts()
void	elaborate(java.lang.Object arg) elaborate(): On elaboration, the inputs of the RAM will be undefined.
void	evaluate(java.lang.Object arg) evaluate(): If either port_nCS or port_nWE are undefined, the RAM data is invalidated, and the DOUT value is undefined.
boolean	resize(int n_words, int n_bits)
void	setBitsPerWord(int n_bits)
void	setSize(int n_words)

Methods inherited from class hades.models.rtlib.memory.GenericMemory

addMemoryListener, addMemoryListenerOld, checkInvalidateMemory, configure, constructStandardValues, createMemory, dataAtAddressIsUndefined, dbg, getAddressBusWidth, getAddrOffset, getBitsPerWord, getConfigDialog, getDataArray, getDataAt, getEnableAnimationFlag, getExternalResources, getHexDigitsPerWord, getHexString, getInstructionDecoder, getPropertySheet, getResourcename, getSize, getToolTip, initialize, initializeWithDefaultValues, initializeWithRandomValues, initializeWithX, initializeWithZeroes, isConnected, main, merge, needsExternalResources, notifyReadListeners, notifyReadListenersOld, notifyWriteListeners, notifyWriteListenersOld, parse, parseLabelLine, parseRAM, removeMemoryListener, removeMemoryListenerOld, save, setDataArray, setDataAt, setEnableAnimationFlag, setEnableAnimationFlag, setInstructionDecoder, setResourcename, toString, warning, write

Methods inherited from class hades.simulator.SimObject

constructDynamicSymbol, copy, getBindkey, getClassLoader, getDebug, getEditor, getFullName, getName, getParent, getPort, getPorts, getResourceAsStream, getSimulator, getSymbol, getSymbolResourceName, getVersionId, isVisible, keyPressed, message, mousePressed, needsDynamicSymbol, setClassLoader, setConsole, setDebug, setEditor, setName, setParent, setPorts, setSimulator, setSymbol, setVersionId, setVisible, tearDown

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

port_A

protected PortStdLogicVector port_A

port_DIN

protected PortStdLogicVector port_DIN

port_DOUT

protected PortStdLogicVector port_DOUT

port_nWE

protected PortStdLogic1164 port_nWE

port_nCS

protected PortStdLogic1164 port_nCS

t_access

public static final double t_access

See Also:

Constant Field Values

t_tristate

public static final double t_tristate

See Also:

Constant Field Values

t_undefined

public static final double t_undefined

See Also:

Constant Field Values

t_setup

public static final double t_setup

See Also:

Constant Field Values

t_min_we_cycle

public static final double t_min_we_cycle

See Also:

Constant Field Values

Constructor Detail

RAM

public RAM()

RAM constructor

Method Detail

constructPorts

protected void constructPorts()

Overrides:

constructPorts in class GenericMemory

canChangeSize

public boolean canChangeSize()

Specified by:

canChangeSize in interface Memory

Overrides:

canChangeSize in class GenericMemory

setSize

public void setSize(int n_words)

Specified by:

setSize in interface Memory

Overrides:

setSize in class GenericMemory

setBitsPerWord

public void setBitsPerWord(int n_bits)

Specified by:

setBitsPerWord in interface Memory

Overrides:

setBitsPerWord in class GenericMemory

resize

public boolean resize(int n_words,
                      int n_bits)

Specified by:

resize in interface Memory

Overrides:

resize in class GenericMemory

elaborate

public void elaborate(java.lang.Object arg)

elaborate(): On elaboration, the inputs of the RAM will be undefined. Correspondingly, the outputs are, too.

Specified by:

elaborate in interface Simulatable

Overrides:

elaborate in class GenericMemory

evaluate

public void evaluate(java.lang.Object arg)

evaluate(): If either port_nCS or port_nWE are undefined, the RAM data is invalidated, and the DOUT value is undefined. If port_nCS is high, the RAM is inactive. That is, the outputs are tristated, and all write requests are ignored. If port_nCS is low, the output is driven with the memory contents of the currently active address. Also, as long as port_nWE is low, the input data is written to the active address.

Warning: The RAM model currently does not check for timing violations or address glitches during write cycles. Instead, the corresponding memory locations are written.

Specified by:

evaluate in interface Simulatable

Overrides:

evaluate in class GenericMemory