Encoding:

POOL32A

000000

index

base

rd

0

LBUX

1000100101

6

5

5

5

1

10

SPECIAL3

011111

base

index

rd

LBUX

00110

LX

001010

6

5

5

5

5

6

Format: 

LBUX rd, index(base)

microMIPSDSP

Load Unsigned Byte Indexed

Purpose:

Load Unsigned Byte Indexed

To load a byte from memory as an unsigned 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 8bit byte at the memory location specified by the aligned effective address are fetched, zero-extended to the GPR register length and placed in GPR rd.

Restrictions:

None.

Operation: 

vAddr31..0 = GPR[index]31..0 + GPR[base]31..0
( pAddr, CCA ) = AddressTranslation( vAddr, DATA, LOAD )
pAddr = pAddrPSIZE-1..2 || ( pAddr1..0 xor ReverseEndian2 )
memwordGPRLEN..0 = LoadMemory ( CCA, BYTE, pAddr, vAddr, DATA )
GPR[rd]63..0 = zero_extend( memword7..0 )

Exceptions:

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