exp43.asm

实现16位DSP TMSC5416 32位浮点数乘法

res_hm .usect "flt_add",1 ;result high mantissa
res_lm .usect "flt_add",1 ;result low mantissa
res_exp .usect "flt_add",1 ;result exponent
res_sign .usect "flt_add",1 ; result sign
op2_hm .usect "flt_add",1 ; OP2 high mantissa
op2_lm .usect "flt_add",1 ; OP2 low mantissa
op2_se .usect "flt_add",1 ; OP2 sign and exponent
op1_se .usect "flt_add",1 ; OP1 sign and exponent
op1_hm .usect "flt_add",1 ; OP1 high mantissa
op1_lm .usect "flt_add",1 ; OP1 low mantissa
op1_msw .usect "flt_add",1 ; OP1 packed high word
op1_lsw .usect "flt_add",1 ; OP1 packed low word
op2_msw .usect "flt_add",1 ; OP2 packed high word
op2_lsw .usect "flt_add",1 ; OP2 packed low word
err_no .usect "flt_add",1 ;
*******************************************************************
* Floating point number 12.0 can be represented as 1100 = 1.100 x 23 => sign =0
* biased exponent = 127+3 = 130
* 130 = 10000010
* Mantissa 10000000000000000000000
* Thus 12.0 can be represented as 01000001010000000000000000000000= 4140h
**********************************************************************************
*
K_OP1_HIGH .set 4140h ; floating point number 12.0
K_OP1_LOW .set 0000h
K_OP2_HIGH .set 4140h ; floating point number 12.0
K_OP2_LOW .set 0000h
	.def start
	.mmregs
	.text	
start:	RSBX C16 ; Insure long adds 
	LD #res_hm,DP ; initialize the page pointer
	LD #K_OP2_HIGH,A ; load floating #2 – 12
	STL A,op2_msw
	LD #K_OP2_LOW,A
	STL A,op2_lsw
	LD #K_OP1_HIGH,A ; load floating #1 – 12
	STL A,op1_msw
	LD #K_OP1_LOW,A
	STL A,op1_lsw
;store result sign	
	ld op1_msw,A
	and #8000h,a
	ld op2_msw,b
	and b,a
	bc sign_0,AEQ
	st #1,res_sign
	b next
sign_0:	st #0,res_sign
;store op1
next: 	dld op1_msw,a
	bc op_zero,AEQ
	stl a,op1_lm
	sth a,-7,op1_se
	and #07fh,16,a
	or #80h,16,a
	sth a,op1_hm
;store op2
	dld op2_msw,a
	bc op_zero,AEQ
	stl a,op2_lm
	sth a,-7,op2_se
	and #07fh,16,a
	or #80h,16,a	
	sth a,op2_hm
;以下逻辑要验证
;caculate expont
	LD op1_se,A ; Load OP1 sign and exponent
	AND #0FFh,A ; Mask OP1 exponent
	LD op2_se,B ; Load OP2 sign and exponent
	AND #0FFh,B ; Mask OP2 exponent
	SUB #07Fh,B ; Subtract offset (avoid double bias)
	ADD B,A ; Add OP1 exponent
	STL A,res_exp ; Save result exponent on stack

;caculate mantissa,32bit unsigned fract multiply
	ld #0,a
	LD op1_lm,T ; load low mant of op1 to T register
	MPYU op2_lm,A ; RS * YZ
	MPYU op2_hm,B ; RS * 0X
	add a,-16,b
	ld op1_hm,t
	mpyu op2_lm,a
	add b,a
	mpyu op2_hm,b
	stl b,res_hm ;low word of 0X*0Q
	add res_hm,16,a;
	sfta a,8,b
	bc step1,nc
	ld a,-1,a;shift right (>=2)
	ld res_exp,b
	add #1,b
	STL b,res_exp ; Save result exponent on stack
step1 
	ld res_exp,b
	BC underflow,BLT ; branch to underflow handler if exp < 0
	SUB #0FFh,b ; test for overflow
	BC overflow,BGT ; branch to overflow is exp > 255
cmant
	stl a,-7,res_lm
	ld a,-7,a
	ld a,-16,a
	and #7fh,a
	stl a,res_hm
	
here
	b here
op_zero:st #0,res_sign
	st #0,res_hm
	st #0,res_lm
	st #0,res_exp
	b here
overflow
	st #0ffh,res_exp
	b cmant
underflow
	st #0,res_exp
	b cmant
	.end