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Introduction
The Digilent AVR Programmer is a Microsoft
Windows
programming of Atmel AVR
It is specifically designed for programming
AVR devices on Digilent products, but is also a
general purpose AVR device programmer for
those AVR devices that support the serial insystem programming protocol.
The AVR Programmer supports the in-system
programming of Atmel AVR devices using a
programming cable connected to a 6-pin
programming connector on the target board.
All Digilent products with a AVR microcontroller
have a suitable connector.
Installation Information
The AVR Programmer is installed by running
the Windows installer application available for
download from the Digilent web site.
The installer will copy the application program
files, required device drivers, AVR Part
Description files, and documentation file to the
user’s computer.
The part description files are copied to the
folder: Program Files\Common
Files\Digilent\AvrParts.
Overview of AVR Microcontrollers
The Atmel AVR devices are 8-bit
microcontrollers with various I/O peripheral
functions and varying amounts of program and
data memory.
There are two different ways that AVR devices
can be programmed. High-voltage parallel
programming involves placing the AVR device
into a special device programmer. This can
only be done before the device is soldered to a
® application used for in-system
® microcontrollers.
l
®
www.digilentinc.com
(509) 334 6306 Voice and Fax
PC board. In-system programming uses a
serial interface and an in-system programming
protocol to program the devices in circuit. Any
AVR device can be programmed using the
parallel programming method. Most, but not all,
AVR devices also support the in-system
programming method. The AVR Programmer
only works with in-system programming.
There are four basic parts of an AVR device
that can be programmed: the program flash,
the data EEPROM, fuses, and lock bits.
The program flash holds program instructions
to be executed. The data EEPROM is nonvolatile memory that can be programmed via
the in-system programming protocol, and can
also be read or written by the program running
on the device. Program flash and data
EEPROM are configured using the Program
tab in the AVR Programmer.
Fuses and lock bits are used to select the
device’s operating modes. They are described
in more detail below.
Before programming the flash or EEPROM
memory, you must first erase the device. When
flash or EEPROM memory are erased, the bits
are set to the 1 state. When programming, 0
bits are programmed to 0 and 1 bits are left
unchanged. It is not possible to program a bit
from 0 to 1. This can only be accomplished by
erasing.
Flash and EEPROM memory can only be
erased and reprogrammed a limited number of
times before they wear out. Atmel rates the
memories in the AVR parts as having an
endurance of 10,000 erase/reprogram cycles.
Programming over already-programmed bits
will wear them out prematurely. The AVR
Programmer allows you to manually erase the
device and has an option to automatically
erase the device while programming.
®
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The file format used to hold the data for
programming the flash and EEPROM
memories is the Intel HEX file format. Intel
HEX is an industry standard file format used
for device programming files. Software
development tools designed to work with AVR
parts produce Intel HEX format files. There are
two files produced by the development tools.
One contains the data to be programmed into
the program flash memory, and the other
contains the data to be programmed into the
data EEPROM. When the AVR Programmer is
used to read back the contents of device
memory, an Intel HEX format file is generated.
Fuses are control bits that establish the basic
operating modes of the device. These control
such things as the clock source, enabling the
watchdog timer, setting compatibility modes,
and so on. The number and meaning of the
fuse bits vary between the different AVR
devices. Device fuses are configured using
the Fuses tab in the AVR Programmer.
Warning! Use caution when setting the clock
source in the fuses. The in-system
programming protocol uses the clock source
currently selected by the fuses to clock the
internal programming state machine. If the
fuses are set to select a non-functioning clock
source (such as the external crystal oscillator
when no crystal is provided on the board), the
in-system programming interface will stop
functioning. This will render the board/device
unusable and usually requires unsoldering the
device from the board and replacing it with a
new, un-programmed, device. AVR devices
come from the factory with the fuses set to use
an internal oscillator to guarantee that the insystem programming interface will work in all
circumstances.
The lock bits are used to lock different parts of
the device memory. This is done to prevent
reprogramming and/or reading back the
contents of memory to prevent the altering or
reverse engineering of a design. Once a lock
bit is set, that portion of the memory can’t be
reprogrammed or read back, depending on the
specific lock bit setting, until the entire device
is erased. The number and meaning of the lock
bits vary between different AVR devices. Lock
bits are configured using the Lock Bits tab in
the AVR Programmer.
Overview of the AVR Programmer
Communication
The AVR in-system programming protocol
uses the serial peripheral interface (SPI) for
the communications channel between the PC
and the device being programmed. Digilent
has two different programming cables that can
be used to provide the communications
interface: the Digilent Parallel JTAG cable and
the Digilent JTAG-USB cable.
Digilent programming cables conform to the
JTAG standard and therefore bear the JTAG
signal names instead of the SPI signal names.
Observe the following label conventions when
connecting the cable to a board:
TMS = SS or RST
TDI = MOSI
TDO = MISO
TCK = SCK
The parallel cable connects to the parallel
printer port on a PC and to the Digilent 6-pin
programming connector on the board being
programmed. The AVR Programmer
implements the SPI interface over the parallel
port. The GIVEIO.SYS device driver must be
installed to provide access to the parallel port.
GIVEIO.SYS is automatically installed when
the AVR programmer is installed.
The JTAG-USB cable connects a USB port on
the PC and the 6-pin connector on the board
being programmed. Firmware in the USB cable
provides the SPI implementation. The AVR
Programmer communicates with the USB
cable using the drivers provided for that cable
(specify the cable on the Programmer Settings
tab).
Device Parameters
The AVR Programmer is designed to work with
any AVR device that supports the in-system
programming protocol. In order to work with
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different devices, the programmer needs to
know certain properties of the device being
programmed. This information can be provided
in one of three ways: Digilent part description
files, Atmel part description files, or manual
settings.
Digilent part description files contain the
required device programming information, plus
additional information used to describe the
fuses and lock bits available. Digilent makes
available a part description file for the AVR
devices used on Digilent product boards.
These are installed when the AVR
Programmer is installed. Additional or updated
device files can be downloaded from the
Digilent web site. The Digilent AVR Part
Description File Specification document is also
available for download. It describes the syntax
conventions used in a Digilent part description
file so that you can create part description files.
See www.digilentinc.com
for more information.
Atmel part description files are installed when
the Atmel AVR Studio application is installed.
These files contain the required device
information and some of the additional
information that describes the fuses and lock
bits available in the device.
If no part description file is available for a
device, you can enter the required information
using the AVR Device Manual Settings fields
on the Device Settings tab. The information to
be entered in these fields can be found in the
Memory Programming section of the part data
sheet for the specific AVR device. AVR part
data sheets can be downloaded from Atmel at
www.atmel.com. When manual settings are
being used, the list boxes in the Fuses and
Lock Bits tabs will be empty. The fuses and
lock bits values must be entered as
hexadecimal values in the Value field.
Complete descriptions for the fuses and lock
bits for a device are found in the Memory
Programming section of the device data sheet.
The AVR Device drop-down list box on the
Program tab lists the available device files and
the manual settings option. Manual Settings is
listed first, followed by the available Digilent
part description files, and then the Atmel part
description files.
The part description files are listed by file name
in the drop-down list box. If two files having the
same name appear in the list, the first one
found will be used. Since the Digilent files are
looked for before the Atmel files, a Digilent file
will override an Atmel file having the same
name.
Signature Bytes
Each AVR device contains a device signature.
This is a three-byte sequence that identifies
the specific device. Before any programming
operation, the AVR programmer checks the
signature bytes read from the device with the
signature bytes for the selected device. If the
signatures don’t match no action is performed.
This prevents accidentally damaging a device
by programming it with data for a different part.
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AVR Programmer User Interface
The user interface of the AVR Programmer has
two main parts. A tabbed dialog box occupies
the upper portion of the window with tabs for
the major functional areas of the program. The
lower portion of the window features a scrolling
status box that gives feedback on the state of
operation of the program.
Program Tab
The Program tab is used for device type
selection and configuring the memories in the
device. It is divided into three sections: AVR
Device, Program Flash, and Data EEPROM.
AVR Device Section
The AVR Device drop-down list box is used to
select the part description file for the AVR
device being programmed, or to choose
manual device settings. Choose the
appropriate selection from the available items
in the list.
This list box contains the Manual Settings
choice, followed by the available Digilent part
description files and the available Atmel part
description files.
The Erase button erases the memory in the
device. For most AVR devices this erases both
the program flash and the data EEPROM.
Some devices have a fuse bit that disables
EEPROM Erase when the device is erased. In
this case erasure of the EEPROM depends on
the setting of this fuse bit.
Program Flash Section
The File drop down list box contains up to
eight of the most recently selected
programming files. The file shown in this list
box is used to program the device.
The browse button is marked with an ellipsis
(…) and displays an Open dialog for browsing
the file system to find a programming file.
The Program button programs the contents of
the selected programming file into the program
flash memory on the device. Depending on the
options selected on the Programmer Settings
tab, the device may be automatically erased
before programming and the device contents
may be read and verified after programming.
The status window reports the actions taken
and their results.
The Verify button reads the contents of the
program flash memory and compares it against
the contents of the selected programming file.
This can be used to verify that the device was
programmed correctly or to determine if the
device is currently programmed with the
contents of a specific file. The verify operation
may not work correctly if the settings of the
lock bits prevent reading back part of the
device memory.
The Read button reads the contents of the
program flash memory and writes it to a file.
When the Read button is clicked, a Save As
dialog box is displayed so that the file can be
named. When the Save button on the Save
File box is clicked, the contents of the program
flash memory are read, converted to Intel HEX
format and written to the specified file. This file
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can then be used to program another device.
The read operation may not work correctly if
the settings of the lock bits prevent reading
back part of the device memory.
Data EEPROM Section
The Data EEPROM section contains the same
user interface elements with the same
functionality as the Program Flash section.
Device Settings Tab
The Device Settings tab is used to examine or
set the device properties used to control the
device programming process. The tab also
contains the controls used to manage the
Internal Oscillator Calibration feature.
AVR Device Manual Settings Section
This section includes several fields containing
the device properties that control the device
programming process. If Manual Settings is
chosen in the AVR Device list box on the
Program tab, then these fields will be active
and you must enter the appropriate values into
these fields. If a part description file is chosen
instead of Manual Settings, then these fields
will be inactive and will display the information
read from the part description file.
For entering the settings manually, the
information needed for these fields can be
found in the “Memory Programming” section of
the data sheet for the specific AVR device.
The Signature Bytes field contains the threebyte signature for the device. If entered
manually, it is entered as three hexadecimal
values separated by spaces. For example, the
signature for an ATmega64 is entered as 0x1E
0x96 0x02 .
The Read button causes the signature to be
read from the device and displayed in the
Signature Bytes field.
The Program Flash Size (bytes) field
specifies the size of the program flash
memory. It is entered as a decimal integer
number.
The Flash Page Size (words) field specifies
the size of the program flash page buffer.
Some AVR devices use a page buffer to hold
pages of program data during the
programming process. This is entered as a
decimal integer number giving the size of the
page buffer in 16-bit words. For AVR devices
that are not paged, the decimal value 1 should
be placed in this field.
The EEPROM Size (bytes) field specifies the
size of the data EEPROM memory. It is
entered as a decimal integer number.
The Number of Fuse Bytes field specifies the
number of fuse bytes in the device. AVR
devices have between one and three fuse
bytes, depending on the specific device.
Internal Oscillator Calibration Section
Most AVR devices have an internal RC
oscillator available as one of the clock sources.
This oscillator can be calibrated using
calibration values written into each device at
the factory. A calibration value is a byte value
that can be written to the calibration register to
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tune the RC oscillator to operate more closely
at its nominal frequency. The calibration values
are stored in a special non-volatile memory
that is not accessible at run time in all devices.
If the oscillator calibration feature is used, it is
typical for the calibration value to be read from
the device and stored in a known location in
memory while programming the device. The
calibration value will then be read from the
known memory location and written to the
calibration register during the startup
initialization of the firmware program running
on the device.
The Internal Oscillator Calibration user
interface provides facilities for reading a
calibration value from the device and writing it
to a specified location in either the program
flash memory or the data EEPROM memory.
The Calibration Frequency drop-down list
box contains the list of calibration values
available for the device.
The Read button reads the selected calibration
value and displays it in the Value field.
The Value field displays the calibration value
read from the device or the value to be written
to the device. If entered manually, it is entered
as a single hexadecimal byte value.
The Address field specifies the memory
address at which the calibration value will be
written. The Program Flash and Data
EEPROM radio buttons select the memory to
which this address refers.
The Write button writes the byte displayed in
the Value field to the specified memory
address.
Fuses Tab
The Fuses tab is used to read and set the fuse
bits in the device. This tab includes a fuses list,
a Value field, and some control buttons.
The fuses list displays the available sets of
fuse bits as described by the selected part
description file. The contents of the fuses list
varies depending on the device selected in the
AVR Device field of the Program tab. Refer to
the device’s Atmel data sheet for a description
of its fuse bits. If Manual Settings is chosen for
the AVR Device, then this list will be empty.
The Value field shows the binary value for the
fuse bytes that corresponds to the current
selections made in the fuses list. The number
of bytes shown corresponds to the number of
fuse bytes defined for the selected AVR
device.
If a part description file is selected in the AVR
Device field of the Program tab, this field is
inactive and merely reports the binary value
corresponding to the selections in the fuses
list. If Manual Settings is chosen in the AVR
Device field of the Program tab, this field is
active and the fuses list will be empty. In this
case, enter the desired value for the fuses as
one to three hexadecimal values (depending
on the number of fuse bytes in the device).
Note that for most fuse bits, setting the bit to 0
enables the function. The values are entered
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with the extended fuse byte first, followed by
the high fuse byte and then the low fuse byte.
The Program button programs the currently
selected fuses into the device.
The Verify button reads the current value of
the fuses from the device and compares them
against the selections in the fuses list.
The Read button reads the value of the fuse
bits from the device and updates the fuses list
and value field.
Lock Bits Tab
The Lock Bits tab is used to read and set the
lock bits in the device. The contents and
operation of the Lock Bits tab is similar to the
Fuses tab.
Programmer Settings Tab
The Programmer Settings tab is used to select
options to control the operation of the AVR
Programmer. The AVR Device Programming
Options are used to enable or disable different
modes of operation of the Programmer. This
tab is also used to select the communications
interface to be used to talk to the device being
programmed.
AVR Device Programming Options Section
The Erase Device Before Programming
checkbox causes the device to be erased
before the flash memory is programmed. No
erase is performed automatically before
programming the data EEPROM, so if this
option is used, you should program the flash
memory before programming the EEPROM. If
this option is disabled, the device should be
erased manually before programming.
The Automatically Verify After
Programming checkbox causes the device
memory (either flash or EEPROM) to be read
and compared against the contents of the
programming file after programming. Any
errors are reported in the status window.
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The Verify After Erase checkbox causes the
contents of the program flash and data
EEPROM to be read back after an erase
operation to verify that the device is properly
erased.
The Automatically Read Device Fuses
When Switching To Fuses Tab checkbox
causes the current fuse setting in the device to
be read and used to set the options in the fuse
list each time the fuses tab is displayed.
The Automatically Read Device Lock Bits
When Switching To Lock Bits Tab checkbox
causes the current lock bits setting in the
device to be read and used to set the options
in the lock bits list each time the lock bits tab is
displayed.
Programmer Settings Section
The Programmer drop-down list box specifies
the Digilent programming cable to use for
communication with the device being
programmed.
The Port drop-down list box specifies the
port/device to use from the available devices
installed in the system. This list box is
populated with the corresponding choices for
the cable selected in the Programmer field.
The Settings drop-down list box specifies the
additional settings needed to configure the
selected communications device.
The Configure button, if enabled, displays a
dialog box for configuring the programming
cable.
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