ARM ARM7TDMI User Manual download pdf (Page 28)

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The <fields> indicate which fields of the CPSR/SPSR be written to should be allowed to

be changed. This limits any changes just to the fields intended by the programmer. The

allowed fields are;

c sets the control field mask bit (bit 16)

x sets the extension field mask bit (bit 17)

s sets the status field mask bit (bit 18)

f sets the flags field mask bit (bit 19)

One or more fields may be specified.

4.21 MUL – Multiply

Syntax:

MUL{<cond>}{S} <Rd >, <Rm>, <Rs>

RTL:

if(cond)

Rd  Rs • Rm

Flags updated if S used:

N, Z (C is unpredictable)

Encoding:

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

cond 0 0 0 0 0 0 0 S Rd SBZ Rs 1 0 0 1 Rm

Usage and Examples:

MUL performs a 32x32 multiply operation, and stores a 32-bit result. Since only the

least significant 32-bits are stored, the result is the same for signed and unsigned

numbers.

The instruction below stores the product of R1 and R2 to R0.

MUL R0, R1, R2

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 ... 42 43

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ARM ARM7TDMI User Manual Page 28