C51: The file order in the project causes errors.

keil suggest that STARTUP.A51 should be last file in the project (should be linked as last)

No. They don't "suggest" that it "should" be last. They flat-out tell you it must be either last or next-to-last (in case you also explicitly include INIT.A51).

keil suggest that STARTUP.A51 should be last file in the project (should be linked as last)

No. They don't "suggest" that it "should" be last. They flat-out tell you it must be either last or next-to-last (in case you also explicitly include INIT.A51).

I know that the STARTUP.A51 file must be last or next-to-last. That was configuration I start with.
I wouldn't write this question if my project behaved according to the instructions.

Maybe I will describe my problem in other words:
In reference to article http://www.keil.com/support/docs/2263.htm, project should behave different when STARTUP.A51 is on last position (like it should be) and when it's anywhere else (where it shouldn't be).
But in my project, it behave different only when it is on first position. The worst is that, it work correct only when STARTUP.A51 is on first position.

We had strange problems beetween two revisions of software, to find out what is the cause, we compared 2 revision of project line by line, change by change.
Position of startup file cause this problems and the project works correctly only if the position of this file is incompatible with the instructions.

do you have any code that specifies location?

Can you tell us if you have any code in your project that specifies location?

Yes, there is a code that reserve space in memory, set CRC value and flash protection.

CSEG AT 17FEh
ProgCRC: DW 4D67h

// conf memory
CSEG AT 1800h
ConfMem: DS 1024

CSEG AT 1DFFh
FlashProtection: DB (~(12))     // First 6KB locked -> 12 pages, 512B each

CSEG AT 1E00h
ReservedFlash: DS 512           // last page of flash

END

The above code is located in separate .a51 file that is linked as last file, in the configuration which behave correct (where Startup.a51 file is linked as first).

which chip?

I would be inclined to take a close look at the map files and in particular check the differences between working and failing.

Zeusti

It's a Silicon Labs C8051F353.

15.1.1. Flash Lock and Key Functions
Flash writes and erases by user software are protected with a lock and key function. The Flash Lock and Key Register (FLKEY) must be written with the correct key codes, in sequence, before Flash operations may be performed. The key codes are: 0xA5, 0xF1. The timing does not matter, but the codes must be written in order. If the key codes are written out of order, or the wrong codes are written, Flash writes and erases will be disabled until the next system reset. Flash writes and erases will also be disabled if a Flash write or erase is attempted before the key codes have been written properly. The Flash lock resets after each write or erase; the key codes must be written again before a

so, when

CSEG AT 1DFFh
FlashProtection: DB (~(12))     // First 6KB locked -> 12 pages, 512B each

get written, to memory you are hosed as far as writing the rest of your code