PM0014 datasheet(20/46 Pages) STMICROELECTRONICS

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Arithmetic library functions

PM0014

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5.3.4

cSub_32

csub_32 (short LeftOpMsb_I, short LeftOpLsb_I, short LeftOpMsb_R,

short LeftOpLsb_R, short RightOpMsb_I, short RightOpLsb_I,

short RightOpMsb_R, short RightOpMsb_I, long *Output)

Description:

Subtraction of two complex 32-bit operands.

Argument:

LeftOpMsb_I

Left operand imaginary part most significant bits.

LeftOpLsb_I

Left operand imaginary part least significant bits.

LeftOpMsb_R

Left operand real part most significant bits.

LeftOpLsb_R

Left operand real part least significant bits.

RightOpMsb_I

Right operand imaginary part most significant bits.

RightOpLsb_I

Right operand imaginary part least significant bits.

RightOpMsb_R Right Operand real part most significant bits.

RightOpLsb_R

Right Operand real part least significant bits.

Output

Output pointer.

Algorithm:

LeftOp_R - RightOp_R = Output_R

LeftOp_I - RightOp_I = Output_I

Note:

Output imaginary part is contained in the highest addresses

(pointed by Output + 4). Output real part is contained in the lowest

addresses (pointed by Output).

Set the MS bit-field of the MCW register to have a saturated result

(signed arithmetic).

Assembly source

code:

cSub_32.asm

Code size and cycles: Size: 52 bytes

Instruction cycles: 25

Test:

Two files are provided to test the function: an input vector file

(cSub_32.in) and an output vector file (cSub_32.res):

cSub_32.in is made as follows:

LeftOpMsb_I1, LeftOpLsb_I1, LeftOpMsb_R1, LeftOpLsb_R1,

RightOpMsb_I1, RightOpLsb_I1, RightOpMsb_R1, RightOpLsb_R1,

...

cSub_32.res is made as follows:

OutputMsb_R1, OutputLsb_R1,

...

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