Assembly masm汇编如何访问结构变量

DPT是一种定义如下的结构：

DPT STRUC
rSrtHdUnld DB 1; Bits 0-3: SRT step rate time, bits 4-7: head unload time.
rDmaHdLd   DB 1; Bit  0: 1=use DMA, bits 2-7: head load time.
bMotorOff  DB 1; 55-ms increments before turning disk motor off.
bSectSize  DB 1; Sector size (0=128, 1=256, 2=512, 3=1024).
bLastTrack DB 1; EOT (last sector on a track).
bGapLen    DB 1; Gap length for read/write operations.
bDTL       DB 1; DTL (Data Transfer Length) max transfer when length not set.
bGapFmt    DB 1; Gap length for format operation.
bFillChar  DB 1; Fill character for format (normally 0f6H).
bHdSettle  DB 1; Head-settle time (in milliseconds).
bMotorOn   DB 1; Motor-startup time (in 1/8th-second intervals)
DPT ENDS ; Size=11.   

mov (DPT PTR [DI-SIZEOF DPT]).bHdSettle,15

在MASM中组装时，我使用了以下语法：

MOVB [DI-SIZEOF DPT]+[DPT.bHdSettle],15

MASM显示以下错误：

syntax error : [

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我不确定

movb

应该是什么，但我认为这是一个打字错误，你的意思是

mov

您可以这样编写指令：

DPT STRUC
rSrtHdUnld DB 1; Bits 0-3: SRT step rate time, bits 4-7: head unload time.
rDmaHdLd   DB 1; Bit  0: 1=use DMA, bits 2-7: head load time.
bMotorOff  DB 1; 55-ms increments before turning disk motor off.
bSectSize  DB 1; Sector size (0=128, 1=256, 2=512, 3=1024).
bLastTrack DB 1; EOT (last sector on a track).
bGapLen    DB 1; Gap length for read/write operations.
bDTL       DB 1; DTL (Data Transfer Length) max transfer when length not set.
bGapFmt    DB 1; Gap length for format operation.
bFillChar  DB 1; Fill character for format (normally 0f6H).
bHdSettle  DB 1; Head-settle time (in milliseconds).
bMotorOn   DB 1; Motor-startup time (in 1/8th-second intervals)
DPT ENDS ; Size=11.   

mov (DPT PTR [DI-SIZEOF DPT]).bHdSettle,15

或者，如果您在

PROC

中，希望通过

di

执行多个结构访问，您可以告诉汇编程序暂时假定

di

指向

DPT

：

ASSUME di:PTR DPT
mov [di-SIZEOF DPT].bHdSettle,15
.....
ASSUME di:NOTHING

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如果这是masm，通常语法类似于

mov[di sizeof dpt].dpt.bHdSettle，15

。为什么di指向结构的结尾，而不是开始？