Samsung S3C2500B User Manual page 172

INSTRUCTION SET
Division and Remainder
A number of divide routines for specific applications are provided in source form as part of the ANSI C library
provided with the ARM Cross development toolkit, available from your supplier. A short general purpose divide
routine follows.
MOV
Div1 CMP
CMPCC
MOVCC
MOVCC
BCC
MOV
Div2 CMP
SUBCS
ADDCS
MOVS
MOVNE
BNE
Overflow Detection in the ARM9TDMI
1. Overflow in unsigned multiply with a 32-bit result
UMULL
TEQ
BNE
2. Overflow in signed multiply with a 32-bit result
SMULL
TEQ
BNE
3. Overflow in unsigned multiply accumulate with a 32 bit result
UMLAL
TEQ
BNE
4. Overflow in signed multiply accumulate with a 32 bit result
SMLAL
TEQ
BNE
3-60
Rcnt,#1
Rb,#0x80000000
Rb,Ra
Rb,Rb,ASL#1
Rcnt,Rcnt,ASL#1
Div1
Rc,#0
Ra,Rb
Ra,Ra,Rb
Rc,Rc,Rcnt
Rcnt,Rcnt,LSR#1
Rb,Rb,LSR#1
Div2
Rd,Rt,Rm,Rn
Rt,#0
overflow
Rd,Rt,Rm,Rn
Rt,Rd ASR#31
overflow
Rd,Rt,Rm,Rn
Rt,#0
overflow
Rd,Rt,Rm,Rn
Rt,Rd, ASR#31
overflow
; Enter with numbers in Ra and Rb.
; Bit to control the division.
; Move Rb until greater than Ra.
; Test for possible subtraction.
; Subtract if ok,
; Put relevant bit into result
; Shift control bit
; Halve unless finished.
; Divide result in Rc, remainder in Ra.
; 3 to 6 cycles
; +1 cycle and a register
; 3 to 6 cycles
; +1 cycle and a register
; 4 to 7 cycles
; +1 cycle and a register
; 4 to 7 cycles
; +1 cycle and a register
S3C2500B