com.cmpware.cmp.links
Class FIFO

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

All Implemented Interfaces:

MemoryMappedIOReader, MemoryMappedIOWriter

Direct Known Subclasses:

CellBE_FIFO

public class FIFO
extends Link

This class implements a synchronous FIFO. This is used as a link component to build inter-processor communication networks. The input port of the FIFO is typically mapped to a memory mapped IO address on one processor and the output port to a memory mapped IO address on another processor. This creates a communication link between the processors. Note that the internal implementation of this link object requires some care to support the multiprocessor simulation environment. All state update should be done at commit time.

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

Author:

SAG

Field Summary

static java.lang.String	copyright Copyright string
static int	DEFAULT_SIZE The default FIFO size
protected int[]	fifo The FIFO data
protected int	head The FIFO 'head' pointer
protected MemoryMappedIOException	mmioe A Memory Mapped IO 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 boolean	readFlag This flag indicates that a read was performed on this cycle
protected int	readStallCount The number of read stalls
protected int	tail The FIFO 'tail' pointer
protected int	writeAddr The write address (for information only)
protected int	writeCount The number of writes
protected int	writeStallCount The number of write stalls
protected boolean	writtenFlag This flag indicates that a write was performed on this cycle

Constructor Summary

FIFO()
This constructor allocates a FIFO using the default FIFO size.

FIFO(int size)
This constructor allocates a FIFO.

Method Summary

int	free() This method returns the number of remaining slots in the FIFO.
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.
protected boolean	isEmpty() This method returns a true if the FIFO is empty and a false otherwise.
protected boolean	isFull() This method returns a true if the FIFO is full and a false otherwise.
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	setBufferSize(int size) This method is used to set the buffer size in the communication 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.
int	used() This method returns the number of used slots in the FIFO.
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

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

DEFAULT_SIZE

public static final int DEFAULT_SIZE

The default FIFO size

See Also:

Constant Field Values

fifo

protected int[] fifo

The FIFO data

head

protected int head

The FIFO 'head' pointer

tail

protected int tail

The FIFO 'tail' pointer

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

writtenFlag

protected boolean writtenFlag

This flag indicates that a write was performed on this cycle

readFlag

protected boolean readFlag

This flag indicates that a read was performed on this cycle

mmioe

protected MemoryMappedIOException mmioe

A Memory Mapped IO Execption (so we don't have to keep re-allocating them)

Constructor Detail

FIFO

public FIFO()

This constructor allocates a FIFO using the default FIFO size.

FIFO

public FIFO(int size)

This constructor allocates a FIFO.

Parameters:

size - the FIFO size.

Method Detail

setBufferSize

public void setBufferSize(int size)

Description copied from class: Link

This method is used to set the buffer size in the communication link. The method defined here does nothing. If the subclass of Link needs the ability to set a buffer size, it should overload this method.

Overrides:

setBufferSize in class Link

Parameters:

size - The buffer size.

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.

used

public int used()

This method returns the number of used slots in the FIFO.

Returns:

This method returns the number of used slots in the FIFO.

free

public int free()

This method returns the number of remaining slots in the FIFO.

Returns:

This method returns the number of remaining slots in the FIFO.

isEmpty

protected boolean isEmpty()

This method returns a true if the FIFO is empty and a false otherwise.

isFull

protected boolean isFull()

This method returns a true if the FIFO is full and a false otherwise.