Class RAM

  extended byhades.simulator.SimObject
      extended byhades.models.rtlib.memory.GenericMemory
          extended byhades.models.rtlib.memory.RAM
All Implemented Interfaces:
java.lang.Cloneable, ContextToolTip, Memory, java.io.Serializable, Simulatable
Direct Known Subclasses:

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 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


protected PortStdLogicVector port_A


protected PortStdLogicVector port_DIN


protected PortStdLogicVector port_DOUT


protected PortStdLogic1164 port_nWE


protected PortStdLogic1164 port_nCS


public static final double t_access
See Also:
Constant Field Values


public static final double t_tristate
See Also:
Constant Field Values


public static final double t_undefined
See Also:
Constant Field Values


public static final double t_setup
See Also:
Constant Field Values


public static final double t_min_we_cycle
See Also:
Constant Field Values
Constructor Detail


public RAM()
RAM constructor

Method Detail


protected void constructPorts()
constructPorts in class GenericMemory


public boolean canChangeSize()
Specified by:
canChangeSize in interface Memory
canChangeSize in class GenericMemory


public void setSize(int n_words)
Specified by:
setSize in interface Memory
setSize in class GenericMemory


public void setBitsPerWord(int n_bits)
Specified by:
setBitsPerWord in interface Memory
setBitsPerWord in class GenericMemory


public boolean resize(int n_words,
                      int n_bits)
Specified by:
resize in interface Memory
resize in class GenericMemory


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
elaborate in class GenericMemory


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
evaluate in class GenericMemory