com.cmpware.cmp.links
Class BroadcastBus

java.lang.Object
  com.cmpware.cmp.Link
      com.cmpware.cmp.links.BroadcastBus

All Implemented Interfaces:

MemoryMappedIOReader, MemoryMappedIOWriter

public class BroadcastBus
extends Link

This class implements a broadcast bus. It has no handshaking and is used to send a single value to multiple inputs. It is completely up to the user to guarantee that synchronization is performed properly. Note that this implementation does a write on commit(). Also note that there may be many readers and writers, with many read and write addresses. Only the last address set is used. On recommendation is to have the read and write ports at consistent addresses across processors, if possible.

Copyright (c) 2005 Cmpware, Inc. All Rights Reserved.

Author:

SAG

Field Summary

static java.lang.String

copyright Copyright string

Constructor Summary

BroadcastBus()

Method Summary

int	getReadAddress() This method returns the processor address to which the read port of this Memory Mapped IO is mapped.
int	getReadCount() This method returns the number of times the read port has been accessed.
int	getReadStallCount() This method returns the number of times the read port has stalled.
int	getValue() This method returns the most recently written value of the Memory Mapped IO.
int	getWriteAddress() This method returns the processor address to which the write port of this Memory Mapped IO is mapped.
int	getWriteCount() This method returns the number of times the write port has been accessed.
int	getWriteStallCount() This method returns the number of times the write port has stalled.
boolean	isReadable() This method returns a true if the Memory Mapped IO is currently readable.
boolean	isWriteable() This method returns a true if the Memory Mapped IO port is currently writeable.
int	read() This method reads a value from the Memory Mapped IO port.
void	readCommit() All Memory Mapped IO reads are performed whenever data is available.
void	reset() This abstract class is used to reset the link.
void	setReadAddress(int addr) This method sets the read address of the Memeory Mapped IO.
void	setWriteAddress(int addr) This method sets the write address of the Memory Mapped IO.
void	write(int val) This method writes a word to the Memory Mapped IO.
void	writeCommit() All Memory Mapped IO writes are performed whenever data is available.

Methods inherited from class com.cmpware.cmp.Link

get, setBufferSize

Methods inherited from class java.lang.Object

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

Field Detail

copyright

public static final java.lang.String copyright

Copyright string

See Also:

Constant Field Values

Constructor Detail

BroadcastBus

public BroadcastBus()

Method Detail

reset

public void reset()

Description copied from interface: MemoryMappedIOReader

This abstract class is used to reset the link. This may be necessary in links that have state.

write

public void write(int val)
           throws MemoryMappedIOException

Description copied from interface: MemoryMappedIOWriter

This method writes a word to the Memory Mapped IO.

Parameters:

val - The value to write to the Memory Mapped IO.

Throws:

MemoryMappedIOException - - this method throws a MemoryMappedIOException if the write could not be completed on this cycle. This will typically cause a stall of the processor and a retry on the next cycle.

read

public int read()
         throws MemoryMappedIOException

Description copied from interface: MemoryMappedIOReader

This method reads a value from the Memory Mapped IO port.

Returns:

This method reads a value from the Memory mapped IO port.

Throws:

MemoryMappedIOException - - this method throws a MemoryMappedIOException if the read could not be completed on this cycle. This will typically cause a stall of the processor and a retry on the next cycle.

writeCommit

public void writeCommit()

Description copied from interface: MemoryMappedIOWriter

All Memory Mapped IO writes are performed whenever data is available. But because this is a multiprocessor simulation environment, it may not be proper to flag this communication resource as "free" until the end of the simulation cycle. This is necessary to preserve clock boundaries in multiprocessor simulation environments. This method should be called at the end of all activity in a simulation cycle and should tag the resource as free as necessary.

readCommit

public void readCommit()

Description copied from interface: MemoryMappedIOReader

All Memory Mapped IO reads are performed whenever data is available. But because this is a multiprocessor simulation environment, it may not be proper to flag this communication resource as "free" until the end of the simulation cycle. This is necessary to preserve clock boundaries in multiprocessor simulation environments. This method should be called at the end of all activity in a simulation cycle and should tag the resource as free as necessary.

setReadAddress

public void setReadAddress(int addr)

Description copied from interface: MemoryMappedIOReader

This method sets the read address of the Memeory Mapped IO. Note that is only provides the adddress value for convenience when displaying Memory Mapped IO status information. This does not effect how the Memory Mapped IO is decoded.

Parameters:

addr - The Memory Mapped IO read address.

getReadAddress

public int getReadAddress()

Description copied from interface: MemoryMappedIOReader

This method returns the processor address to which the read port of this Memory Mapped IO is mapped.

Returns:

This method returns the processor address to which the read port of this Memory Mapped IO is mapped.

getReadCount

public int getReadCount()

Description copied from interface: MemoryMappedIOReader

This method returns the number of times the read port has been accessed.

Returns:

This method returns the number of times the read port has been accessed.

getReadStallCount

public int getReadStallCount()

Description copied from interface: MemoryMappedIOReader

This method returns the number of times the read port has stalled.

Returns:

This method returns the number of times the read port has stalled.

setWriteAddress

public void setWriteAddress(int addr)

Description copied from interface: MemoryMappedIOWriter

This method sets the write address of the Memory Mapped IO. Note that is only provides the adddress value for convenience when displaying Memory Mapped IO information. This does not effect how the Memory Mapped IO port is decoded.

Parameters:

addr - The Memory Mapped IO write address.

getWriteAddress

public int getWriteAddress()

Description copied from interface: MemoryMappedIOWriter

This method returns the processor address to which the write port of this Memory Mapped IO is mapped.

Returns:

This method returns the processor address to which the write port of this Memory Mapped IO is mapped.

getWriteCount

public int getWriteCount()

Description copied from interface: MemoryMappedIOWriter

This method returns the number of times the write port has been accessed.

Returns:

This method returns the number of times the write port has been accessed.

getWriteStallCount

public int getWriteStallCount()

Description copied from interface: MemoryMappedIOWriter

This method returns the number of times the write port has stalled.

Returns:

This method returns the number of times the write port has stalled.

getValue

public int getValue()

Description copied from interface: MemoryMappedIOReader

This method returns the most recently written value of the Memory Mapped IO. Note that this value may or may not have already been read.

Returns:

This method returns the most recently written value of the Memory Mapped IO. Note that this value may or may not have already been read.

isReadable

public boolean isReadable()

Description copied from interface: MemoryMappedIOReader

This method returns a true if the Memory Mapped IO is currently readable. A false is returned otherwise.

Returns:

This method returns a true if the Memory Mapped IO is currently readable. A false is returned otherwise.

isWriteable

public boolean isWriteable()

Description copied from interface: MemoryMappedIOWriter

This method returns a true if the Memory Mapped IO port is currently writeable. A false is returned otherwise.

Returns:

This method returns a true if the Memory Mapped IO port is currently writeable. A false is returned otherwise.