BRA syntax?
02-26-2005, 12:40 PM
#1
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BRA syntax?
From what I can tell. BRA $xxxx will work and the assembler will calc the offset and put it into a +-128d for you correct?
But how do you do it if your not sure of the exact address?
BRA #xxx?
The pink book says 2's complement???
I'm slowly working on relocatable code so I need to change all the Bxx/jmp's to the numerical offset I think.
But how do you do it if your not sure of the exact address?
BRA #xxx?
The pink book says 2's complement???
I'm slowly working on relocatable code so I need to change all the Bxx/jmp's to the numerical offset I think.
02-26-2005, 01:49 PM
#2
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You really want to use labels. Counting bytes and changing them everytime the code is touched is error prone. With labels the code will still be relocatable as a BRA is relative to the current PC register.
The max distance for a BRA is +127 bytes and -128 bytes. A backwards BRA is in 2's complement. A forward BRA is in direct bytes.
RBob.
The max distance for a BRA is +127 bytes and -128 bytes. A backwards BRA is in 2's complement. A forward BRA is in direct bytes.
RBob.
02-26-2005, 06:14 PM
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Yep. Labels are your friend, as well as the pseudo mneumonic, ORG available in most assemblers. With all lables and origins of teh code fixed, you can make widespread changes and just assemble the code. The compiler will do all the addresses and offsets automatically.
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