Process Identifier Register - 2024.2 English

The Process Identifier Register (PID) is used to uniquely identify a software process during MMU address translation. It is controlled by the C_USE_MMU configuration option on MicroBlaze. The register is only implemented if C_USE_MMU is greater than 1 (User Mode) and C_AREA_OPTIMIZED is set to 0 (Performance) or 2 (Frequency).

When accessed with the MFS and MTS instructions, the PID is specified by setting Sa = 0x1000. The register is accessible according to the memory management special registers parameter C_MMU_TLB_ACCESS.

PID is also used when accessing a TLB entry:

• When writing Translation Look-Aside Buffer High (TLBHI) the value of PID is stored in the TID field of the TLB entry.
• When reading TLBHI and MSR[UM] is not set, the value in the TID field is stored in PID.

The following figure illustrates the PID register and the following table provides bit descriptions and reset values.