Encoding:

SW32

111110

rt

base

offset

6

5

5

16

Format: 

SW rt, offset(base)

microMIPS

Store Word

Purpose:

Store Word

To store a word to memory.

Description: 

 memory[GPR[base] + offset] = GPR[rt]

The least-significant 32-bit word of GPR rt is stored in memory at the location specified by the aligned effective address. The 16-bit signed offset is added to the contents of GPR base to form the effective address.

Restrictions:

Pre-Release 6: The effective address must be naturally-aligned. If either of the 2 least-significant bits of the address is non-zero, an Address Error exception occurs.

Release 6 allows hardware to provide address misalignment support in lieu of requiring natural alignment.

Note: The pseudocode is not completely adapted for Release 6 misalignment support as the handling is implementation dependent.

Operation: 

vAddr = sign_extend(offset) + GPR[base]
(pAddr, CCA) = AddressTranslation (vAddr, DATA, STORE)
pAddr = pAddrPSIZE-1..3 || (pAddr2..0 xor (ReverseEndian || 02))
bytesel = vAddr2..0 xor (BigEndianCPU || 02)
datadoubleword = GPR[rt]63-8*bytesel..0 || 08*bytesel
StoreMemory (CCA, WORD, datadoubleword, pAddr, vAddr, DATA)

Exceptions:

TLB Refill, TLB Invalid, TLB Modified, Address Error, Watch