Register to set up the limit address of DMA-protected high-memory region. This register must be set up before enabling protected memory through PMEN_​REG, and must not be updated when protected memory regions are enabled

This register is always treated as RO for implementations not supporting protected high memory region (PHMR field reported as Clear in the Capability register)

The alignment of the protected high memory region limit depends on the number of reserved bits (N:0) of this register. Software may determine the value of N by writing all 1s to this register, and finding most significant zero bit position below host address width (HAW) in the value read back from the register. Bits N:0 of the limit register is decoded by hardware as all 1s

The protected high-memory base & limit registers functions as follows

• Programming the protected low-memory base and limit registers with the same value in bits HAW:(N+1) specifies a protected low-memory region of size 2(N+1) bytes
• Programming the protected high-memory limit register with a value less than the protected high-memory base register disables the protected high-memory region

Software must not modify this register when protected memory regions are enabled (PRS field Set in PMEN_​REG).