STM32F303CB Unique Device ID - false values?

Forum|Forum|10 years ago
April 27, 2016
4 replies
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Posted on April 27, 2016 at 15:48

Hi

I am reading from different STM32F303CB the unique device IDs as follows:

// unique device ID base address from RM p.1120 
 #define BASE_ADDR_UID ((uint32_t *)0x1FFFF7AC) 
uint32_t UID_Low = BASE_ADDR_UID[0]; 
uint32_t UID_Mid = BASE_ADDR_UID[1]; 
uint32_t UID_High = BASE_ADDR_UID[2];

I got following values:

UID_High

UID_Mid

UID_Low

uC 1

20 34 36 34

57 32 57 07

0025 0023

uC 2

20 34 36 34

57 32 57 07

001F 002F

uC 3

20 34 36 34

57 32 57 04

0022 0036

uC 4

20 36 35 32

50 33 57 11

003F 0026

There is a description in the reference manual, what these values mean:

http://www2.st.com/content/ccc/resource/technical/document/reference_manual/4a/19/6e/18/9d/92/43/32/DM000435pdf/files/DM000435pdf/jcr:content/translations/en.DM000435pdf

UID [31:0]: X/Y coordinates on Wafer (BCD coded) UID [39:32]: Wafer number (8-bit unsigned number) UID [95:40]: LOT number (ASCII encoded) Problem: In my UID_Low shall be the X/Ycoordinates coded inBCD. But 0xF in BCD does not exist. In addition, the highest byte of the LOT number is a space (0x20). Is the reference manual information false or am I doing/understanding something wrong? I hope you can help me. Thank you and best regards #unique-device-id-96bit-uid-stm32

This topic has been closed for replies.

troy1818

Associate III

Posted on April 29, 2016 at 09:09

BCD is just stupid, that it is used today is even more stupid.

But of course, you are right, there is no 0xF in BCD since it would defeat the whole purpose with the encoding. If you get these values as you say, then:

1. Typo in reference manual

2. Error when reading flash (wrong number of wait states configured?)

3. Error/corrupted flash

4. ST used some other strange BCD format which nobody heard of.

Regards,

Rygelxvi

re.wolff9

Senior

Posted on April 30, 2016 at 11:36

It is a ''typo'' in the manual. They mean something completely different. It is a sign-magnitude number. If the highest bit is set, the rest is a number in the 0-50 range indicating the magnitude of the negative number.

So 0x800a is -10.

Like you my first ten chips did not have negative numbers....

Your lot is something like 'W2W 464' You should read them as ASCII, although you somehow have a non-ascii character in there....