9S12XDP512, What is address 0x7FFF0F used for?

[Pitsch]

Hallo

When I program a MC9S12XDP512 the address 0x7FFF0F is set to 0xFE. But this address isn’t defined in the s19-File. The address 0x7FFF0F is placed just in front of the vector addresses.

Is this 0xFE default value for the address 0x7FFF0F? What is this address used for?

[Franky_TJ_]

the 0x7Fff0f address is the security byte and its programmed by the debbuger by default after mass erase with 0xfe. after each reset this byte is read by and loaded into the Flash security Register @ 0x101. and if last two bits are not '10'  the Flash is secured and the debugger cant access any of the flash data.

CHECK CHAPTER 30

Message Edited by Franky_TJ_ on 2006-10-1811:44 AM

Message Edited by Franky_TJ_ on 2006-10-1811:45 AM

[DannyM83]

0x7FFF0F is the is the security byte, detailed fully in chapter 30 of the manual.

Basically changing this value to anything other than FE will cause the devices flash to become inaccessible to a debugger.

Danny

[CrasyCat]

Hello

As far as I can tell global address 0x7FFF0F  is equivalent to address 0xFF0F.

This is the location for the register  Flash Security Register (FSEC).

CrasyCat