ADE75 datasheet(107/148 Pages) AD

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Preliminary Technical Data

ADE75xx/ADE71xx

Rev. PrE | Page 107 of 148

Remark:

The read protection does not prevent MOVC

commands from being executed within the code.

There is an additional layer of protection offered by a protection

security key. The user can setup a protection security key so that

the protection scheme cannot be changed without this key.

Once the protection key has been configured, it may not be

modified.

Enabling Flash Protection by Code

The protection byts in the Flash can be programmed using

Flash controller command and programming ECON to 0x08.

The EADRH, EADRL, PROTB1 and PROTB0 bytes are used in

this case to store the data to be written to the 32 bits of write

protection. Note that the EADRH and EADRL registers are not

used as data pointers here, but to store write protection data.

PROTR

PROTKY

PROTB0

PROTB1

EADRL

EADRH

31-28

27-24

23-20

19-16

15-12

11-8

7-4

3-0

PROTECTION KEY[7:0]

0x3FFF

0x3FFE

0x3FFD

0x3FFC

0x3FFB

0x3FFA

0x3FF9

0x3E00

WDOG

LOCK

Figure 68: Flash Protection in Page 31

The sequence for writing the protection bits is:

Set up the EADRH, EADRL, PROTB1 and PROTB0

registers with the write/erase protection bits. When

erased, the protection bits default to 1, like any other

bit of Flash memory. The default protection setting is

for no protection. To enable protection, write a 0 to the

bits corresponding to the pages that should be

protected.

Set up the PROTR register with the read protection

bits. Note that every read protection bit protects four

pages. To enable the read protection bit, write a 0 to

the bits that should be read protected.

To enable the protection key, write to the PROTKY

to modify the protection scheme. The protection key,

flash memory address 0x3FFA defaults to FFH so if

the PROTKY register is not written to, it will remain

0xFFH. If the protection key is written to, the

PROTKY register must be written with this value

every time the protection functionality is accessed.

Note that once the protection key is configured, it

cannot be modified. Also note that the most

significant bit of 0x3FFA is used to enable a lock

mechanism for the watchdog settings—see the

Watchdog Timer section for more information.

Run the protection command by writing 08H to the

ECON register.

Reset the chip to activate the new protection.

To enable read and write/erase protection for the last page only,

use the following 8051 code. Writing the flash protection

command to the ECON register initiates programming the

protection bits in the flash.

; enable write/erase protection on the last page only

MOV EADRH, #07FH

MOV EADRL, #0FFH

MOV PROTB1, #FFH

MOV PROTB0, #FFH

; enable read protection on the last four pages only

MOV PROTR, #07FH

; set up a protection key of 0A3H. This command can be

; omitted to use the default protection key of 0xFF

MOV PROTKY, #0A3H

; write the flash key to the FLSHKY register to enable flash

; access. The flash access key is not configurable.

MOV FLSHKY, #3BH

; write flash protection command to the ECON register

MOV ECON, #08H

Enabling Flash Protection by emulator

commands

Another way to set the Flash protection bytes is to use some

reserved emulator commands available only in download mode.

These commands write directly to the SFRs and can be used to

duplicate the operation mentioned in the Enabling Flash

Protection by Code paragraph. Once these Flash bytes are

written, the part can exit emulation mode by reset and the

protections will be effective. This method can be used in

production and implemented after downloading the program.

The commands used for this operation are an extension of the

commands listed in the application note uC004 –

Understanding the Serial Download Protocol:

- Command with ASCII code ‘I’ or 0x49 write the data into R0

- Command with ASCII code ‘F’ or 0x46 write R0 into the SFR

address defined in the data of this command

Omitting the protocol defined in uC004, the sequence to load

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