Hi,
The S12P has 8B size Device ID at the global address 0x0_4000 – 0x0_4007. The local address of Device ID starts at 0x8000, PAGE = 01.
However, you can use for your own serial number Program Once Filed with 64B size at the global address 0x0_40C0 – 0x0_40FF
See 13.4.5.6 Program Once Command in the reference manual.
I hope it helps you.
Best regards,
Diana