我正在尝试编写一个程序，将一个数字从ieee转换为TNS（大端），反之亦然。 我对ARM和装配很新。我没有收到错误，它只是没有按预期工作，如果有人能看到它，我会很感激。每一行都有注释，这里实际讨论的子程序是“unpack ieee”程序，它没有按预期工作，我看不出原因。编辑：IEEE和TNS数字有3个部分，我试图使用掩码“抓住”或分离3个部分。解压缩程序使用掩码将每个部件放入单独的寄存器中，以便我可以操作每个部件以进行转换。目前我正在尝试通过调用它来确认解压缩过程是否有效，然后打印寄存器。这些数字要么不打印，要么打印不正确的结果。结束编辑我还没有编写转换例程，但我有一个psudocode算法，如果你愿意，我可以发布。如果您还有其他想知道的事，请告诉我。代码：
AREA Conversion, CODE
SWI_WriteC EQU &0 ;output character in r0
SWI_WriteL EQU &2 ;output String in r0
SWI_Exit EQU &11 ;finish program
ENTRY
ADR r0, STRING ;load string
SWI SWI_WriteL ;print string
LDR r1, IEEE ;load IEEE num into r0
BL Print ;print number
BL UnpackIEEE ;call UnpackIEEE subroutine
ADR r1, r4 ;
BL Print
SWI SWI_Exit ;finish
UnpackIEEE
LDR r1, SMASK ;load the sign bit mask into r1
LDR r2, EMASK ;load the exponent mask into r2
LDR r3, GMASK ;load the significand mask into r3
AND r4, r0, r1 ;apply sign mask to IEEE and save into r4
AND r5, r0, r2 ;apply exponent mask to IEEE and save into r5
AND r6, r0, r3 ;apply significand mask to IEEE and save into r6
MOV pc, r14 ;return
ConvToTNS
Print MOV r2,#8 ;count of nibbles = 8
LOOP MOV r0,r1,LSR #28 ;get top nibble
CMP r0, #9 ;hexanumber 0-9 or A-F
ADDGT r0,r0, #"A"-10 ;ASCII alphabetic
ADDLE r0,r0, #"0" ;ASCII numeric
SWI SWI_WriteC ;print character
MOV r1,r1,LSL #4 ;shift left one nibble
SUBS r2,r2, #1 ;decrement nibble count
BNE LOOP ;if more nibbles,loop back
MOV pc, r14 ;return
IEEE DCD 0x40280000 ;2.75 or 40,280,000
TNS DCD 0x28000101 ;2.75 or 28,000,101
SMASK DCD 0x80000000 ;Sign bit mask
EMASK DCD 0x7F800000 ;Exponent mask
GMASK DCD 0x007FFFFF ;Significand mask
STRING DCB "HI THERE",0
END
答案 0 :(得分：0)
我想我知道你想要实现的目标。
我写了一个使用十进制数15.75的程序 该号码以IEEE754格式存储 它首先转换为TNS格式，转换后的数字将打印到控制台。 然后将该数字转换回IEEE745格式。 转换后的数字将打印到控制台，然后程序退出。
该程序是为ARM7编写的。
如果听起来像是你想要实现的代码，请查看代码：
ENTRY
LDR r0, IEEE ; Load IEEE formatted # into r0
BL ieeetotns ; Branch to IEEE to TNS conversion subroutine
BL Print ; Branch to print number to console
BL tnstoieee ; Branch to TNS to IEEE conversion subroutine
BL Print ; Branch to print number to console
SWI SWI_Exit ; Exit Program
; Load IEEE Masks into registers
ieeetotns LDR r1, SIGNMASK ; Load sign mask into r1
LDR r2, IEEEEXPMASK ; Load IEEE exponent mask into r2
LDR r3, IEEESIGMASK ; Load IEEE significand mask into r3
; Convert from IEEE to TNS
AND r4, r0, r1 ; unpack sign bit, store in R4
AND r5, r2, r0 ; initial unpack of exponent, store in r5
MOV r5, r5, LSR #23 ; shift exponent right 23 bits
ADD r5, r5, #129 ; add 129(10) to exponent to correct excess encoding for TNS
AND r6, r3, r0 ; initial unpack of significand, store in r6
ADD r6, r7, r6, LSL #8 ; shift significand left 8 bits, kill off LSB
ORR r0, r4, r5 ; pack sign and exponent
ORR r0, r0, r6 ; pack significand with sign and exponent,
; r0 now holds IEEE to TNS converted word
MOV PC, LR ; Return to main subroutine
; Load TNS Masks
tnstoieee LDR r1, SIGNMASK ; Load sign mask into r1
LDR r2, TNSSIGMASK ; Load TNS Significand mask into r2
LDR r3, TNSEXPMASK ; Load TNS Exponent mask into r3
; Convert back to IEEE
AND r4, r0, r1 ; unpack sign bit
AND r5, r2, r0 ; initial unpack of significand, store in r5
MOV r5, r5, LSR #8 ; Shift significand right 8 bits
AND r6, r3, r0 ; Initial unpack of exponent, store in r6
SUB r6, r6, #129 ; Subtract 129 to correct excess encoding
ADD r6, r7, r6, LSL #23 ; Shift exponent left 23 bits
; Pack the converted number into r0
ORR r0, r4, r5 ; Pack sign and significand
ORR r0, r0, r6 ; Pack exponent with sign and significand,
; r0 now holds TNS to IEEE converted word
MOV PC, LR ; Return to main subroutine
Print MOV r2, #8 ; Count of nibbles = 8
MOV r1, r0 ; Move number to r1
MOV r3, r0 ; Store converted number in r3 for later
LOOP MOV r0, r1, LSR #28 ; Get top nibble
CMP r0, #9 ; Hex number 0-9 or A-F?
ADDGT r0, r0, #"A"-10 ; ASCII A-F
ADDLE r0, r0, #"0" ; ASCII 0-9
SWI SWI_WriteC ; Print character to console
MOV r1, r1, LSL #4 ; Shift left one nibble
SUBS r2, r2, #1 ; Decrement nibble count
BNE LOOP ; If more nibbles loop again
MOV r0, #10 ; Load 10 into r0, ASCII code for carriage return
SWI SWI_WriteC ; Print carriage return to console
MOV r0, r3 ; Move converted number back to r0
MOV PC, LR ; Return to main subroutine
IEEE DCW 0x0000, 0x417C ; IEEE Representation of 15.75(10), 417C0000(16),
; 01000001011111000000000000000000(2)
TNS DCW 0x0103, 0x7C00 ; TNS Representation of 15.75(10), 7C000103(16),
; 01111100000000000000000100000011(2)
; This is not used in program, simply here for comparison of conversions
SIGNMASK DCW 0x0000, 0x8000 ; Mask for sign bit
IEEEEXPMASK DCW 0x0000, 0x7F80 ; Mask for IEEE Exponent
IEEESIGMASK DCW 0xFFFF, 0x007F ; Mask for IEEE Significand
TNSSIGMASK DCW 0xFE00, 0x7FFF ; Mask for TNS Significand
TNSEXPMASK DCW 0x01FF, 0x0000 ; Mask for TNS Exponent
END