Samsung S3C2440A User Manual download pdf (Page 120)

S3C2440A RISC MICROPROCESSOR ARM INSTRUCTION SET

LOADING A WORD FROM AN UNKNOWN ALIGNMENT

; Enter with address in Ra (32 bits) uses

; Rb, Rc result in Rd. Note d must be less than c e.g. 0,1

BIC Rb,Ra,#3 ; Get word aligned address

LDMIA Rb,{Rd,Rc} ; Get 64 bits containing answer

AND Rb,Ra,#3 ; Correction factor in bytes

MOVS Rb,Rb,LSL#3 ; ...now in bits and test if aligned

MOVNE Rd,Rd,LSR Rb ; Produce bottom of result word (if not aligned)

RSBNE Rb,Rb,#32 ; Get other shift amount

ORRNE Rd,Rd,Rc,LSL Rb ; Combine two halves to get result

Samsung S3C2440A User Manual Page 120