C8051F850-C-GM Datasheet, PDF (75/328 Pages) Silicon Laboratories – Low-Cost 8-bit MCU Family with up to 8 kB of Flash

11. Device Identification and Unique Identifier
The C8051F85x/86x has SFRs that identify the device family, derivative, and revision. These SFRs can be
read by firmware at runtime to determine the capabilities of the MCU that is executing code. This allows
the same firmware image to run on MCUs with different memory sizes and peripherals, and dynamically
change functionality to suit the capabilities of that MCU.
In addition to the device identification registers, a 32-bit unique identifier (UID) is pre-programmed into all
Revision C and later devices. The UID resides in the last four bytes of XRAM (C8051F850/1/3/4 and
C8051F860/1/3/4) or RAM (C8051F852/5 and C8051F862/5). For devices with the UID in RAM, the UID
can be read by firmware using indirect data accesses. For devices with the UID in XRAM, the UID can be
read by firmware using MOVX instructions. The UID can also be read through the debug port for all
devices.
Firmware can overwrite the UID during normal operation, and the bytes in memory will be automatically
reinitialized with the UID value after any device reset. Firmware using this area of memory should always
initialize the memory to a known value, as any previous data stored at these locations will be overwritten
and not retained through a reset.
Table 11.1. UID Implementation Information
Device
C8051F850
C8051F851
C8051F853
C8051F854
C8051F860
C8051F861
C8051F863
C8051F864
C8051F852
C8051F855
C8051F862
C8051F865
Memory Segment
Addresses
XRAM
(MSB) 0x00FF, 0x00FE, 0x00FD, 0x00FC (LSB)
RAM (indirect)
(MSB) 0xFF, 0xFE, 0xFD, 0xFC (LSB)
Rev. 1.0
64