Analog Devices ee-55 Application Notes

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Interfacing Byte Programmed

Flash Memories to the

ADSP-2106x SHARC series

Contributed by S.H. 20-Jul-99

Introduction:

Until recently, an EPROM was chosen as
standard external boot memory to start up the
processor in the system. However, if you needed to
change the data of your EPROM, you had unseal
your product, remove the EPROM from the system,
erase it by exposing it to hard UV-light, reprogram it
using a dedicated EPROM burner. Finally, it could be
fitted back into the device.

As this is a complicated and time consuming
procedure, a better solution is to update the code or
data while the non-volatile memory component
remains in the system. This is a key issue for todays
embedded designs, where system specifications and
requirements are continuously updated, especially in
systems, where you have to save application data in a
simple and efficient fashion during runtime.

With the advent of FLASH memories, it is
now possible to save data permanently and update it
when necessary without removing the component
from the system. FLASH memories are also an asset
in systems that need to save data during a power
outage or brownout . The DSP can store its code/data
contents from volatile internal memory to an external,
non-volatile memory, and on revival of the system,
rewrite the old information back to the DSP.

This Engineering Note demonstrates how to
interface a FLASH memory to the ADSP-2106x
SHARC series using a spare memory segment for
FLASH writes. The supplied code shows you how to
access FLASH devices, using AMD NOR FLASHs as
example components, and how to perform the
standard operations like read, write, erase and
system identification.

FLASH Wiring:

As the set-up for data unpacking and
handling the unlock sequences is time consuming
and complicated using DMA write operations, the
update of the FLASH is handled by the core
processor. Therefore to allow core reads and writes
and to access the FLASH during system boot, it is
necessary to connect logically the boot memory
strobe (~BMS) and one of the four available memory
strobes (~ MSx) for the core accesses. The wiring for
8bit wide FLASH memories and the ADSP-21060/ 61/
62 can be found in Figure 1, while Figure 2 is for the
connection using an ADSP-21065L. Please note that
the amount of address lines required is dependent on
the size of the FLASH.

DSP FLASH

A[0..A20*] A[0..A20*]

D[16..23] D[0..7]

~BMS & ~MSx ~CE

~WR ~WE

~RD ~OE

Figure 1. ADSP-21060 / 61 / 62 -> FLASH Wiring

DSP FLASH

A[0..A20*] A[0..A20*]

D[0..7] D[0..7]

~BMS & ~MSx ~CE

~WR ~WE

~RD ~OE

Figure 2. ADSP-21065L -> FLASH Wiring

During system boot, the ADSP sees the
FLASH as an EPROM and uses its standard DMA
booting mechanism by asserting ~BMS and data
packing from 8bit to 48bit.

Basic AMD NOR FLASH Operation:

The AMD FLASH memory space is splitted
into a several sectors , each sector can be protected
individually. This allows to have an emergency set-up
if the previous program code exchange failed for some
reason. Additionally this gives safety for applications

a

where the FLASH is used for both, system booting
and data written to it during program execution. The
sector boundaries are invisible for read / write,
resulting is seamless operation across sector
boundaries, easing the use of the FLASH.

The AMD FLASH uses a byte-by-byte
programming protocol, typical for NOR FLASH types.
A series of command words are written to the FLASH
(using ADSP-2106x core writes in this example),
essentially “unlocking” the device so the proper
information can be stored or retrieved.

The following operations, called Embedded
Programming Algorithms, can be performed on an
AMD FLASH:

Autoselect:

Returns the manufacturer, model number,

and the protection status of any sector.

Byte Write:

Programs a single data word (8 or 16bit wide)

into an unprotected FLASH sector.

ADSP-21060/ 61/ 62 has configurable banks,
defaulting to 8kwords. Keep in mind, to assert the
proper ~MSx signal, it is important to set the MSIZE
bits in the SYSCON register of the IOP processor
accordingly, so that the full addressable area of
FLASH memory fits into a single external memory
bank.

Flash Server Definitions:

Attached to this paper are a number of
software modules used for accessing and controlling
i.e. the AMD29LV010, AMD29LV020, AMD20LV040,
and AMD29F040 FLASH memories, just to name few
devices. This software offers six entry points in the
server code that are function names for FLASH
operations. Before using the functions, some global
definitions (#define LABEL), placed in the software
header, have to be set up to match your FLASH
component. These are:

Sector Erase:

Erases a sector of unprotected memory.

Chip Erase:

Erases all unprotected sectors on a FLASH.

Sector Protect:

Returns status of sector protection bit for the
requested sector on the FLASH.

Please consult the appropriate AMD Data
Sheet for more memory programming information and
for 16bit wide I/O operations.

FLASH access using the external port:

All transactions to memory mapped
peripherals are handled by the 32bit wide external port
of the ADSP-2106x SHARC. As the FLASH memory
is only 8bits or 16bits wide, only the lower data lines
will carry relevant data. Unused data lines will present
the last value the bus was driven to and have to be
masked out. Additionally the ~RD or ~WR line are
asserted and the corresponding memory strobe
~MSx.

The ADSP-21065L offers fixed external
memory blocks, each 16Mwords large, while the

mem_offset:

0x400000 /* default for 21060/61/62 */
This value is the offset to the external
memory, so that the memory corresponding
strobe ~MSx can be asserted by the core
processor. Permissible values for the ADSP­21065L are 0x20000, 0x1000000, 0x2000000
or 0x3000000.

memory_bank:

0x0 /* memory bank 0, ~MS0 */

Needs to be set for setting the wait states in
the WAIT register. Permissible values range
from 0x0 to 0x3.

To successfully start the embedded programming
algorithms, an unlock sequence, a combination of
address and data values has to be written first to the
FLASH. Ulock1_a(ddress) and Ulock1_b(yte)
represent the first combination of address- and data
word, while Ulock2_a(ddress) and Ulock2_b(byte) are
the second pair. Ulock1 and Ulock2 can be changed
depending on the FLASH type and connection
(8/16bit). Please consult the AMD FLASH memory
datasheet for the applicable listing of unlock address /
word combinations.

ulock1_a:

0x5555 /* default for 8bit wide */

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ulock1_b:

0x00AA /* default for 8bit wide */

ulock2_a:

0x2AAA /* default for 8bit wide */

ulock2_b:

0x0055 /* default for 8bit wide */

Flash Server Software:

These API functions provided by the FLASH
software are listed and described below:

In order to make the flash server code “visible” to pre­existing code in other modules, the subroutines that
will be used must be declared as external functions.
This can be done by including the header file flash.h
into your calling program.

After the flash server module (listing 1), a
small example program is given (listings 2-4), showing
how to implement the FLASH programming software.
For more information on linking and calling functions
located in separate modules, please refer to the

ADSP-21000 Family Assembler Tools and Simulator
Manual.

flash_setup:

Sets the number of wait states in external
memory segment.

prog_byte:

Unlocks and writes the value of d_byte into
the FLASH at address.

sect_erase:

Erases one sector of the FLASH starting at
address.

flash_erase:

Erases the complete FLASH.

flash_ident:

Returns in d_byte the vendor code and
device ID. Some FLASH components return
in register r12 the boot block location.

sect_protect:

Return information whether sector at address
was protected during the programming cycle.

More information on each of these functions,
including the parameters that are passed into each
subroutine is included in the comments of the
supplied code. As additional reference, please
consult the FLASH memory datasheet.

FLASH Caveats:

Byte Programming Approach:

You cannot correctly program a byte of data
in the FLASH memory unless the contents of that
memory cell first equals 0xFF. Essentially, a byte
program only converts a logic ‘1’ to a logic ‘0’. A
sector or chip erase operation is the only operation
that allows to set back a logic ‘0’ to a logic ‘1’.
Reprogramming a cell without erasing it may cause
an error condition flagged by the FLASH server in the
status variable error.

Additional Information:

For more information about interfacing ADSP­218x DSPs to various FLASH|es, please consult the
following sources:

ADSP-2100 Family User’s Manual
ADSP-2100 Family Assembler Tools and Simulator

Manual
http://www.analog.com
http://www.amd.com

To apply the FLASH server code, it must be

assembled first and linked into your calling software.

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/****************************************************************************

ANALOG DEVICES
EUROPEAN DSP APPLICATIONS

FLASH API server for memory mapped AMD FLASH Devices

History:

1.0.1.0 15-JUN-99 HS

****************************************************************************/

/****************************************************************************
Below stated defines represent the memory where the FLASH memory device is
connected to and must be changed accordingly to reflect the actual device
pleacement. Please consult the ADSP-2106x USER'S MANUAL to figure out the
correct values for memory offset to the external memory bank and by what
strobes the FLASH can be accessed.
****************************************************************************/

#define mem_offset 0x400000 /* offset to memory bank of FLASH */
#define memory_bank 0x2 /* selected memory bank */

/****************************************************************************
Ulock1_a and Ulock1_b represent the first combination of address and data
required to access the embedded algorithm. Ulock2_a and Ulock2_b are the
second pair of address and data to enter embedded algorithms. Ulock1_a and
Ulock2_a can change depending on the FLASH type and connection (8/16bit).
Please consult the AMD Flash memory datasheet for a complete listing.
****************************************************************************/
#define ulock1_a 0x5555
#define ulock1_b 0x00AA

#define ulock2_a 0x2AAA
#define ulock2_b 0x0055

#define u_mem1_a ulock1_a + mem_offset
#define u_mem2_a ulock2_a + mem_offset

/****************************************************************************
The global definition exports the functions and the labels to a calling
main program.
****************************************************************************/
.global flash_setup; /* entry to memory setup */
.global prog_byte; /* entry to program a byte */
.global sect_erase; /* entry to erase a sector */

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Notes on using Analog Devices’ DSP, audio, & video components from the Computer Products Division

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