最近看到一篇TI官方文档SPRACD《Application Report SPRACD0–December 2017 C2000™ Unique Device Number》,提到常用的C2000器件,都有32位的内部唯一ID,从F280x到F281x到F2803x到2833x,基本覆盖了目前常用的C2000芯片。
不过文档中又提了4条限制,除了2.1.2,其余几条都蛮致命的,尤其是2.1.3和2.1.4,想用它来做产品序列号可以吗?
2.1.1 Variability
The 32-bit value is not a pseudo randomly generated number, but is instead based on simple serialization
algorithms. Devices manufactured near the same time may have the same or similar MSWs, but should
typically have unique LSWs. Under typical situations, LSWs may repeat within a few hundred devices or a
few thousand. By using the MSW and LSW together the probability that a device number is repeated is
greatly reduced.
2.1.2 Static Bits
Some of the bits within the 32-bit value will generally have a fixed value of zero. Static bits reduce the
possible values for the 32-bit number. There is one static bit in the MSW and four static bits in the LSW.
2.1.3 Long-Term Reliability
The 32-bit value is not guaranteed to remain consistent across all operating conditions for the full life of
the device. If the value is used, it should be copied into an on-chip, nonvolatile location, such as the user
one-time programmable (OTP) memory or flash.
2.1.4 Not Tested
Devices are not rejected during factory test based on the 32-bit value. The consequence is that multiple
devices may be programmed with a common value, particularly all bits being zero or one, or some other
nonstandard value.