com.cmpware.cmp.links
Class SharedRegister

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

All Implemented Interfaces:

MemoryMappedIOReader, MemoryMappedIOWriter

Direct Known Subclasses:

CellBE_SharedRegister

public class SharedRegister
extends Link

This class implements a shared register. This is a single register which has a semaphored read / write. This register may be mapped to a memory address or to a special instruction in the processor. To better support a multiprocessor communication environment, this shared registers have some specific properties. First, the register uses hardware semaphores. A write sets the the semaphore and a read clears it. Methods are provided to see if registers are currently readable / writable. This lets reliable, synchronized communication to be performed via these registers. Finally, all data written to registers is "shadowed" until a "commit" call is made. This is necessary in multiprocessor simulation environments to assure that proper clock boundaries are preserved.

Copyright (c) 2004 Cmpware, Inc. All Rights Reserved.

Author:

SAG

Field Summary

static java.lang.String	copyright Copyright string
protected MemoryMappedIOException	mmioe A Shared Register Execption (so we don't have to keep re-allocating them)
protected int	readAddr The read address (for information only)
protected int	readCount The number of reads
protected int	readStallCount The number of read stalls
protected long	shreg The shared register
protected long	shregShadow The shared shadow registers
protected int	writeAddr The write address (for information only)
protected int	writeCount The number of writes
protected int	writeStallCount The number of write stalls

Constructor Summary

SharedRegister()

Method Summary

protected long	clear(long i) This method clears a semaphore in a register value.
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.
protected boolean	isSet(long i) This method tests to see if the semaphore for the register is set.
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.
protected long	set(long i) This method sets a semaphore in a register value.
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

shreg

protected long shreg

The shared register

shregShadow

protected long shregShadow

The shared shadow registers

readAddr

protected int readAddr

The read address (for information only)

writeAddr

protected int writeAddr

The write address (for information only)

readCount

protected int readCount

The number of reads

writeCount

protected int writeCount

The number of writes

readStallCount

protected int readStallCount

The number of read stalls

writeStallCount

protected int writeStallCount

The number of write stalls

mmioe

protected MemoryMappedIOException mmioe

A Shared Register Execption (so we don't have to keep re-allocating them)

Constructor Detail

SharedRegister

public SharedRegister()

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.

isSet

protected boolean isSet(long i)

This method tests to see if the semaphore for the register is set. If it is set a true is returned, otherwise a false is returned.

Returns:

This method tests to see if the semaphore for a register is set. If it is set a true is returned, otherwise a false is returned.

set

protected long set(long i)

This method sets a semaphore in a register value.

Parameters:

i - The value on which to set the semaphore.

Returns:

The value of the input paramater i with its semaphore set.

clear

protected long clear(long i)

This method clears a semaphore in a register value.

Parameters:

i - The value on which to clear the semaphore.

Returns:

The value of the input paramater i with its semaphore cleared.