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SA-1110 Developer’s Manual 61
Coprocessors
See Chapter 5, “Caches, Write Buffer, and Read Buffer” for details on the use and operation of the
read buffer.
Note: The write buffer must be flushed prior to loading the read buffer to maintain coherency between the
two buffers. But, if user-mode MCR access is enabled for the read buffer and the flush is attempted
while in user mode, an undefined instruction exception will occur. In this case, the exception
handler must perform the write buffer flush, then return to user mode to execute the read buffer
load. Alternatively, an SWI instruction can be used as a service call to flush the write buffer.
6.2.11 Registers 10 – 12 RESERVED
Accessing registers 10 – 12 may yield unpredictable results.
6.2.12 Register 13 – Process ID Virtual Address Mapping
The SA-1110 supports the remapping of virtual addresses through a process ID (PID) register. The
6-bit PID value is OR’ed with bits 30..25 of the virtual address when bits 31..25 of the virtual
address are zero. This effectively remaps the address to one of 64 “slots” in the lower 2 Gbyte
address space. The following table shows the OPC_2 and CRm field encodings used to access the
process ID register. This register is zero at reset and if left unmodified, effectively disables the
remapping function. As such, no explicit enable or disable function is necessary. Reserved bits read
as zero and must be written as zero. This register is readable and writable.
The following figure shows the format of the process ID register.
Load Buffer 2 with one word 0b010 0b0010 Virtual address
Load Buffer 2 with four words 0b010 0b0110 Virtual address
Load Buffer 2 with eight words 0b010 0b1010 Virtual address
Load Buffer 3 with one word 0b010 0b0011 Virtual address
Load Buffer 3 with four words 0b010 0b0111 Virtual address
Load Buffer 3 with eight words 0b010 0b1011 Virtual address
Disable user-mode MCR access 0b100 0b0000 Ignored
Enable user-mode MCR access 0b101 0b0000 Ignored
Function OPC_2 CRm Data
Function OPC_2 CRm
Access process ID register 0b000 0b0000