SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
32-Bit Floating-Point Subtraction
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 lower 16-bits of the mantissa are assumed to be all 0. |
MRb | CLA floating-point source register (MR0 to R1) |
LSW: IIII IIII IIII IIII
MSW: 0111 1000 0000 baaa
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 lower 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 accepts 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;
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:
This is a single-cycle instruction.
; 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