HC12DG128A jumps to wrong adress

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HC12DG128A jumps to wrong adress

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mawetzel
Contributor I
We are developing products based on the (very old) MC912DG128ACPVE.
 
I've got ONE exemplar of HC12DG128A that has the following behavior. At a point during startup there's the following code (start12.c):
 
start12.lst:
 345:        (*_startupData.main)();
0010 4bfb0000     CALL  [_startupData:1,PCR]
0014 20ea         BRA   *-20 ;abs = 0000
after linkage:
0x4236  CALL [0x0003, PC] --> jump into the function at adress [0x423D] = "page 1, 0xADB7"
Executing this command (Step into) yield to jump to "page 1, 0xEDB7".
 
Loading a different firmware revision:
0x4236  CALL [0x0003, PC] --> jump into the function at adress [0x423D] = "page 1, 0xAA2D"
Executing this command (Step into) yield to jump to "page 1, 0xEA2D".
 
--> Same behavior.
 
What is wrong here? Simply one board defect? If this would be the only problem, I would have dropped the board but we are facing a 10-30% failure rate on our boards: One or two pages got lost after programming with supplier's IC-Tester. Reprogramming these boards is possible. Now the question is: Does the upper processor bug relate to our 10-30%failure?
 
Processor Description:
MC912DG128ACPVE
0L05H
QQJL0622
 
I didn't find a direct relationship to the errata.pdf.
 
Thanks for your help.
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kef
Specialist I
Did you check what's in memory at 0x423d. When it jumps to page1, EDB7, is there AD.B7.01 in memory at 423d or indeed ED.B7.01?
 
Hm, 10-30% of bad boards, are you using external memory? Bad flash programming algorithm?
 
 
".. one or two pages got lost .." . Does it mean one of 32k flash array got self erased ? If so then check how fast does oscilator start up. Make sure that /RESET is kept low while oscilator isn't stable.
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mawetzel
Contributor I
Thank you.
 
As it might be of interest to others the flash self-erase-issue is threaded separately under subject
"16k Flash Arrays Self-Erased".
 
The answer to your question is yes: In the respective memory (0x423D) really were the three bytes
AD B7 01
resp. (different firmware)
AA 2D 01.
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kef
Specialist I
Then I'm not sure what happens. Looks like CPU got crazy or something makes it unable to read flash memory properly? Overclocked? No more ideas
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