Serial Bootloader for MC56F8025 and 35

[Koch]

Hello,

we are able to build a static bootloader using the CodeWarrior MCU for MC56F8025. Thanks for your help here

Now we do face the difficulty that we want the same bootloader (same srecord) also to work with MC56F8035.

Both controller differ in flash: The 8035 starts at 0x0000. The 8025 starts at 0x4000. This leads to the issue that if one flashes the bootloader meant for the 8025 onto the 8035 the flash at 0x0000 stays at 0xFF up until 0x4000. The bootloader on the 8035 starts nevertheless. (The production bootloader on the other hand, which comes shipped with the 8035, has JMP instructions as described here at 0x0000) 

We could not find anything in the RM what is expected behaviour with 0xFF in pflash.

Can you confirm that this is not an issue? Is flash written with 0xFF just skipped at boot up or is this a coincidence that this works? 

Thanks and greetings!

[Koch]

Hi XiangJun Rong,

Thanks for your quick reply.

Could you also tell me what would be the expected behaviour for MC56F8035 if the JMP to entrypoint is not written at 0x0000 but only at 0x4000? As I wrote, it miraculously works also without this JMP at 0x0000.

Can this maybe achieved with the Vector Base Address Register (VBA)?

greetings.

[xiangjun_rong]

Hi,

I suppose that you have to write the P:0x0000 or P:0x0002 flash location with jmp instructions, they are entry point after Reset. If the data in address P:0x0000 or P:0x0002 are 0xFFFF, the chip will hang on. The VBA register default value is 0x0000 after Reset.

Hope it can help you

BR

XiangJun Rong

[Koch]

Hi XiangJun Rong,

This is also my understanding. BUT i have a MC56F8035 with 0xFF at 0x0000-0x4000. The JMP instructions are only at 0x4000 and it starts flawlessly. And i would like to understand why!

greetings

Koch

[xiangjun_rong]

Hi, Christian,

Frankly speaking, I can not explain either. I trust the data sheet, the data sheet of MC56F8035 says that the boot location is from P:0x0000 rather than P:0x4000.

I have not the MC56F8035 board, so I can not have a test.

Pls try to develop a LED toggling application, locate all the code to P:0x0000, then check if the application can run or not in stand along mode.

BR

XiangJun Rong

[xiangjun_rong]

Hi, Christian,

For MC56F8035, the on-chip flash ranges from 0x0000 to 0x7FFF, totally 64KB. After Reset the PC will point to address 0x0000 and execute from 0x0000, you have to locate the bootloader to the high address of the on-chip, on the 0x0000 P flash, you should put JMP instruction and jump to the bootloader entry point.

Hope it can help you

BR

XiangJun Rong