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To decrement the value in one byte field by one.

 
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Pankaj Shrivastava
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PostPosted: Sat Jul 25, 2009 1:31 am    Post subject: To decrement the value in one byte field by one.
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I have a one byte field in the input file . The value could be a hexadecimal from 00 to 99 .

I have to decrement the value by 1 and update the 1 byte field with new value.

What is the most efficient and shortest way of doing it in assembler .Please help with the code.
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enrico-sorichetti

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PostPosted: Sat Jul 25, 2009 1:41 am    Post subject: Reply to: To decrement the value in one byte field by one.
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post what You have devised, and we' ll comment on it

this is a help forum, not a do it for me one icon_smile.gif
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Pankaj Shrivastava
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PostPosted: Sat Jul 25, 2009 1:56 am    Post subject:
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Ok Enric icon_smile.gif

This is what i have designed :

SR R5,R5
IC R5,VAR1BYTE
SH R5,=H'1'
STC R5,VAR1BYTE


Your comment please.
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Bill O'Boyle

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PostPosted: Sat Jul 25, 2009 2:04 am    Post subject: Reply to: To decrement the value in one byte field by one.
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Looks OK. You can eliminate the 2-Byte H'1' Literal by using -

Code:

AHI R5,-1    SUBTRACT 1 FROM R5 (CC SET)

or you can use -

Code:

BCTR R5,0    SUBTRACT 1 FROM R5 (CC NOT SET)

There isn't any SHI, so using the AHI adding a negative 1 will work.

FWIW, BCTR R0,0 will not work....

Bill
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Pankaj Shrivastava
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PostPosted: Sat Jul 25, 2009 2:08 am    Post subject:
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Thx Bill icon_smile.gif
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