Datasheet

ManualsBrandsANALOG DEVICES ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller LQFP 80 (12x12) 16/32-Bit 41.78 MHz I/O number 40

Data Sheet ADuC7124/ADuC7126

Rev. C | Page 45 of 108

for serial downloading via the I

C. A USB-to-I

C download

dongle can be purchased from Analog Devices, Inc. This board

connects to the USB port of a PC and to the I

C port of the

ADuC7126. The part number is USB-I2C/LIN-CONV-Z.

The AN-806 Application Note describes the protocol for serial

downloading via the I

C in more detail.

JTAG Access

The JTAG protocol uses the on-chip JTAG interface to facilitate

code download and debug.

To access the part via the JTAG interface, the P0.0/BM pin must

be set high.

When debugging, user code should not write to the P0.1, P0.2,

and P0.3 pins. If user code toggles any of these pins, JTAG debug

pods are not able to connect to the ADuC7124/ADuC7126.

If this happens, mass erase the part using the UART/I

downloader.

FLASH/EE MEMORY SECURITY

The 126 kB of Flash/EE memory available to the user can be

read and write protected. Bit 31 of the FEE0PRO/FEE0HID

MMR protects the 126 kB from being read through JTAG and in

UART programming mode. The other 31 bits of this register

protect writing to the Flash/EE memory; each bit protects four

pages, that is, 2 kB. Write protection is activated for all access types.

FEE1PRO and FEE1HID, similarly, protect the second 64 kB

block. All 32 bits of this are used to protect four pages at a time.

Three Levels of Protection

• Protection can be set and removed by writing directly into

FEExHID MMR. This protection does not remain after reset.

• Protection can be set by writing into FEExPRO MMR. It

takes effect only after a save protection command (0x0C)

and a reset. The FEExPRO MMR is protected by a key to

avoid direct access. The key is saved once and must be

entered again to modify FEExPRO. A mass erase sets the

key back to 0xFFFF but also erases all the user code.

• Flash can be permanently protected by using the FEExPRO

MMR and a particular key value of 0xDEADDEAD.

Entering the key again to modify the FEExPRO register is

not allowed.

Sequence to Write the Key

1. Write the bit in FEExPRO corresponding to the page to be

protected.

2. Enable key protection by setting Bit 6 of FEExMOD (Bit 5

must equal 0).

3. Write a 32-bit key in FEExADR and FEExDAT.

4. Run the write key command 0x0C in FEExCON; wait for

the read to be successful by monitoring FEExSTA.

5. Reset the part.

To remove or modify the protection, the same sequence is used

with a modified value of FEExPRO. If the key chosen is the

value 0xDEAD, the memory protection cannot be removed. Only a

mass erase unprotects the part, but it also erases all user code.

The sequence to write the key is illustrated in the following

example (this protects writing Page 4 to Page 7 of the Flash):

FEExPRO=0xFFFFFFFD; //Protect Page 4 to

Page 7

FEExMOD=0x48; //Write key enable

FEExADR=0x1234; //16 bit key value

FEExDAT=0x5678; //16 bit key value

FEExCON= 0x0C; //Write key command

The same sequence should be followed to protect the part

permanently with FEExADR = 0xDEAD and FEExDAT =

0xDEAD.

FLASH/EE CONTROL INTERFACE

Table 37. FEE0STA Register