Encoding:

EXTEND

11110

Imm[10:5]

Imm[15:11]

SWSP

11010

rx

sel = 1

Imm[4:0]

5

5

5

5

5

3

3

Format: 

SW rx, immediate(gp)

MIPS16e2

Store Word (GP-relative) Extended

Purpose:

Store Word (GP-relative) Extended

To store a word to memory.

Description: 

memory[GPR[gp] + immediate] = GPR[rx]

The 16-bit immediate value is sign-extended, then added to the contents of GPR 28 to form the effective address. The contents of GPR rx are stored at the effective address.

Restrictions:

Unpredictable prior to MIPS16e2. 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.

Operation: 

vAddr = sign_extend(immediate) + GPR[28]
(pAddr, CCA) = AddressTranslation (vAddr, DATA, STORE)
dataword = GPR[Xlat(rx)]
StoreMemory (CCA, WORD, dataword, pAddr, vAddr, DATA)

Exceptions:

TLB Refill, TLB Invalid, TLB Modified, Bus Error, Address Error