问一下ADDAB/ADDAH指令问题，谢谢 ADDAB, ADDAH, 指令

slshan@163.com

问一下ADDAB/ADDAH指令问题：
书上例子写着：ADDAB .D1 A4,A2,A4
执行前：A2=0000000BH,A4=00000100H,AMR=00020001H
执行后：A2=0000000BH,A4=00000103H,AMR=00020001H
ADDAH .D1 A4,A2,A4
执行前：A2=0000000BH,A4=00000100H,AMR=00000000H
执行后：A2=0000000BH,A4=00000106H,AMR=00000000H
为什么呀，小弟有点不明白？，特此请教！谢谢！ [em08]

urans2002

我也想知道啊，有高人指点吗

wen_zl

我也不是很懂啊！～呵呵


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yingjunbee

继续问这个问题，有人会吗？

[em01]

zqf8748

ADDAB (.unit) src2, src1, dst

src1 is added to src2 using the byte addressing
mode specified for src2. The addition defaults to linear mode. However, if src2
is one of A4−A7 or B4−B7, the mode can be changed to circular mode by
writing the appropriate value to the AMR .The
result is placed in dst.

AMR:

1−0 A4 MODE 0−3h Address mode selection for register file A4.
            0  Linear modification (default at reset)
            1h Circular addressing using the BK0 field
            2h Circular addressing using the BK1 field
            3h Reserved

ADDAB .D1 A4,A2,A4

ADDAB (.unit) src2, src1, dst

src1 is added to src2 using the byte addressing
mode specified for src2. The addition defaults to linear mode. However, if src2
is one of A4−A7 or B4−B7, the mode can be changed to circular mode by
writing the appropriate value to the AMR .The
result is placed in dst.

AMR:

1−0 A4 MODE 0−3h Address mode selection for register file A4.
            0  Linear modification (default at reset)
            1h Circular addressing using the BK0 field
            2h Circular addressing using the BK1 field
            3h Reserved

ADDAB .D1 A4,A2,A4

A2=0000000BH(A2[0-1]==3),src2==A4-->A4[0-1]=3,the mode changed...and the result is placed in dst(A4).in other words,if(src2==[A4-A7,B4-B7]){A4'[0-1]=A2[0-1];A4=A4';}

[此贴子已经被作者于2007-5-21 16:30:15编辑过]