Encoding:

POOL32S

010110

index

base

rd

0

LDX

0110100101

6

5

5

5

1

10

SPECIAL3

011111

base

index

rd

LDX

01000

LX

001010

6

5

5

5

5

6

Format: 

LDX rd, index(base)

microMIPSDSP

Load Doubleword Indexed

Purpose:

Load Doubleword Indexed

To load a doubleword value from memory as a signed value, using indexed addressing.

Description: 

 rd = memory[base+index]

The contents of GPR index is added to the contents of GPR base to form an effective address. The contents of the 64bit word at the memory location specified by the aligned effective address are fetched and placed in GPR rd.

Restrictions:

The effective address must be naturally-aligned. If any of the three least-significant bits of the address are non-zero, an Address Error exception occurs.

Operation: 

vAddr63..0 = GPR[index] + GPR[base]
if ( vAddr2..0 != 03 ) then
   SignalException( AddressError )
endif
( pAddr, CCA ) = AddressTranslation( vAddr, DATA, LOAD )
doubleword63..0 = LoadMemory ( CCA, DOUBLEWORD, pAddr, vAddr, DATA )
GPR[rd]63..0 = doubleword63..0

Exceptions:

Reserved Instruction, DSP Disabled, TLB Refill, TLB Invalid, Bus Error, Address Error, Watch