MSUBF32 MRa, #16FHi, MRb
32-Bit Floating-Point Subtraction
Operands
MRa
CLA floating-point destination register (MR0 to R1)
#16FHi
A 16-bit immediate value that represents the upper 16-bits of an
IEEE 32-bit floating-point value. The low 16-bits of the mantissa
are assumed to be all 0.
MRb
CLA floating-point source register (MR0 to R1)
Opcode
LSW: IIII IIII IIII IIII
MSW: 0111 1000 0000 baaa
Description
Subtract MRb from the floating-point value represented by the immediate operand. Store
the result of the addition in MRa.
#16FHi is a 16-bit immediate value that represents the upper 16-bits of an IEEE 32-bit
floating-point value. The low 16-bits of the mantissa are assumed to be all 0. #16FHi is
most useful for representing constants where the lowest 16-bits of the mantissa are 0.
Some examples are 2.0 (0x40000000), 4.0 (0x40800000), 0.5 (0x3F000000), and -1.5
(0xBFC00000). The assembler will accept either a hex or float as the immediate value.
That is, the value -1.5 can be represented as #-1.5 or #0xBFC0.
MRa = #16FHi:0 - MRb;
Flags
This instruction modifies the following flags in the MSTF register:
Flag
TF
ZF
NF
LUF
LVF
Modified
No
No
No
Yes
Yes
The MSTF register flags are modified as follows:
• LUF = 1 if MSUBF32 generates an underflow condition.
• LVF = 1 if MSUBF32 generates an overflow condition.
Pipeline
This is a single-cycle instruction.
Example
; Y = sqrt(X)
; Ye = Estimate(1/sqrt(X));
; Ye = Ye*(1.5 - Ye*Ye*X*0.5)
; Ye = Ye*(1.5 - Ye*Ye*X*0.5)
; Y = X*Ye
;
_Cla1Task3:
MMOV32 MR0, @_x ; MR0 = X
MEISQRTF32 MR1, MR0 ; MR1 = Ye = Estimate(1/sqrt(X))
MMOV32 MR1, @_x, EQ ; if(X == 0.0) Ye = 0.0
MMPYF32 MR3, MR0, #0.5 ; MR3 = X*0.5
MMPYF32 MR2, MR1, MR3 ; MR2 = Ye*X*0.5
MMPYF32 MR2, MR1, MR2 ; MR2 = Ye*Ye*X*0.5
MSUBF32 MR2, #1.5, MR2 ; MR2 = 1.5 - Ye*Ye*X*0.5
MMPYF32 MR1, MR1, MR2 ; MR1 = Ye = Ye*(1.5 - Ye*Ye*X*0.5)
MMPYF32 MR2, MR1, MR3 ; MR2 = Ye*X*0.5
MMPYF32 MR2, MR1, MR2 ; MR2 = Ye*Ye*X*0.5
MSUBF32 MR2, #1.5, MR2 ; MR2 = 1.5 - Ye*Ye*X*0.5
MMPYF32 MR1, MR1, MR2 ; MR1 = Ye = Ye*(1.5 - Ye*Ye*X*0.5)
MMPYF32 MR0, MR1, MR0 ; MR0 = Y = Ye*X
MMOV32 @_y, MR0 ; Store Y = sqrt(X)
MSTOP ; end of task
Control Law Accelerator (CLA)
696
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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