com.dalsemi.system
Class DataPort

java.lang.Object
  |
  +--com.dalsemi.system.DataPort

public class DataPort

extends Object

This class allows byte wide reads and writes to memory mapped IO devices.

Two modes are available: Sequential and FIFO (First In First Out). Sequential mode is the default and automatically increments the address after each byte when block reads and writes occur. FIFO access only writes to the specified address, and does not increment the address during block reads and writes. setFIFOMode should be called to set the appropriate mode. After each read or write call, the memory address is returned to the start address designated by setAddress.

For slower memory devices, the use of stretch cycles access may be needed. Set this parameter via setStretchCycles.

Eight chip enables are available, CE0-CE3, PCE0-PCE3.
The memory map is divided into two segments.
CE decoded address space spans from 0 - 4MB: 0x00000000 - 0x003FFFFF
PCE decoded address space spans from 8MB - 12MB: 0x00800000 - 0x00BFFFFF

Expected Transfer Speeds
Function	Speed (bytes/s)
to CE Sequential	655000
to PCE Sequential	172000
to CE FIFO	655000
to PCE FIFO	172000
single byte only	770

Field Summary

int	address Starting memory address for mapped IO access.
int	latchValue The last written value.
static byte	STRETCH0 Use to set the number of memory bus cycles to 2.
static byte	STRETCH1 Use to set the number of memory bus cycles to 3.
static byte	STRETCH10 Use to set the number of memory bus cycles to 12.
static byte	STRETCH2 Use to set the number of memory bus cycles to 4.
static byte	STRETCH3 Use to set the number of memory bus cycles to 5.
static byte	STRETCH7 Use to set the number of memory bus cycles to 9.
static byte	STRETCH8 Use to set the number of memory bus cycles to 10.
static byte	STRETCH9 Use to set the number of memory bus cycles to 11.
byte	stretchCycles Number of stretch memory cycles to use when accessing memory mapped IO.
boolean	useFIFOAccess Set to true to access FIFO type devices.

Constructor Summary

DataPort()
Creates a DataPort object with address of 0x000000.

DataPort(int address)
Creates a DataPort object using the address specified.

Method Summary

int	getAddress() Gets the starting address for read/write.
boolean	getFIFOMode() Gets the FIFO mode.
int	getStretchCycles() Gets the number of stretch memory cycles to use when accessing memory mapped IO.
int	read() Reads a single byte from the address.
int	read(byte[] arr, int off, int len) Reads bytes into an array starting at the address.
int	readLatch() Reads the current latch value.
void	setAddress(int address) Sets the starting address for read/write.
void	setFIFOMode(boolean useFIFOAccess) Sets/Clears the FIFO mode.
void	setStretchCycles(byte stretch) Sets the number of stretch memory cycles to use when accessing memory mapped IO.
void	write(byte[] arr, int off, int len) Writes an array of bytes starting at the address.
void	write(int value) Writes a single byte to the address.

Methods inherited from class java.lang.Object

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

Field Detail

STRETCH0

public static final byte STRETCH0

Use to set the number of memory bus cycles to 2.

STRETCH1

public static final byte STRETCH1

Use to set the number of memory bus cycles to 3.

STRETCH2

public static final byte STRETCH2

Use to set the number of memory bus cycles to 4.

STRETCH3

public static final byte STRETCH3

Use to set the number of memory bus cycles to 5.

STRETCH7

public static final byte STRETCH7

Use to set the number of memory bus cycles to 9.

STRETCH8

public static final byte STRETCH8

Use to set the number of memory bus cycles to 10.

STRETCH9

public static final byte STRETCH9

Use to set the number of memory bus cycles to 11.

STRETCH10

public static final byte STRETCH10

Use to set the number of memory bus cycles to 12.

address

public int address

Starting memory address for mapped IO access.

useFIFOAccess

public boolean useFIFOAccess

Set to true to access FIFO type devices.

latchValue

public int latchValue

The last written value.

stretchCycles

public byte stretchCycles

Number of stretch memory cycles to use when accessing memory mapped IO. Valid values are:
STRETCH0
STRETCH1
STRETCH2
STRETCH3
STRETCH7
STRETCH8
STRETCH9
STRETCH10

Constructor Detail

DataPort

public DataPort()

Creates a DataPort object with address of 0x000000.

DataPort

public DataPort(int address)

Creates a DataPort object using the address specified.

Parameters:

address - address location for read/write.

Method Detail

readLatch

public int readLatch()

Reads the current latch value. This is always the last value written. To read the current value of the pin, call the read method.

Returns:

latch value

read

public int read()
         throws IllegalAddressException

Reads a single byte from the address.

Returns:

byte read

Throws:

IllegalAddressException - if address is out of range

read

public int read(byte[] arr,
                int off,
                int len)
         throws IllegalAddressException

Reads bytes into an array starting at the address.

Parameters:

arr - array of bytes

off - starting offset to read into

len - length to read

Returns:

number of bytes read

Throws:

IllegalAddressException - if address is out of range

write

public void write(int value)
           throws IllegalAddressException

Writes a single byte to the address.

Parameters:

value - single byte to write

Throws:

IllegalAddressException - if address is out of range

write

public void write(byte[] arr,
                  int off,
                  int len)
           throws IllegalAddressException

Writes an array of bytes starting at the address.

Parameters:

arr - array of bytes

off - starting offset to send

len - length to send

Throws:

IllegalAddressException - if address is out of range

setAddress

public void setAddress(int address)

Sets the starting address for read/write.

Parameters:

address - address for read/write

getAddress

public int getAddress()

Gets the starting address for read/write.

Returns:

address for read/write

setFIFOMode

public void setFIFOMode(boolean useFIFOAccess)

Sets/Clears the FIFO mode.

Parameters:

useFIFOAddress - false for automatic incrementing of address during multiple reads, or true for FIFO style non-incrementing addressing

getFIFOMode

public boolean getFIFOMode()

Gets the FIFO mode.

Returns:

true if using FIFO mode, false if using sequential mode

setStretchCycles

public void setStretchCycles(byte stretch)
                      throws IllegalArgumentException

Sets the number of stretch memory cycles to use when accessing memory mapped IO. Valid values are:
STRETCH0
STRETCH1
STRETCH2
STRETCH3
STRETCH7
STRETCH8
STRETCH9
STRETCH10

Parameters:

stretch - stretch cycle value

Throws:

IllegalArgumentException - if stretch is out of range

getStretchCycles

public int getStretchCycles()

Gets the number of stretch memory cycles to use when accessing memory mapped IO.

Returns:

stretch cycle value