There are two kinds of jump instructions. Absolute and relative.
Jump to address if condition code cc is true. Otherwise advance the program counter to the next instruction.
Address is a direct 16 bits address. You can jump to any address from 0 - 64k
Add relative address to programcounter if condition code cc is true. Otherwise advance the program counter to the next instruction.>
Address is a relative 8 bits address. You can only jump between -128 or +127.
Note: You can use JR with labels like this: JR my_label since the assembler will take care of calculating the relative address.
If you always want to jump no matter what you don't have to specify a condition code, but if you only want to jump when a certain set of contitions are met you need to add one of these codes.
Note: You can only have one condition code per jump instruction.
|Hex||Mnemonic||Definition||Flag Test Operation|
|1||LT||Less Than||(S XOR V)=1|
|2||LE||Less Than or Equal||(Z OR (S XOR V)) = 1|
|3||ULE||Unsigned Less Than or Equal||(C OR Z) = 1|
|7||ULT||Unsigned Less Than||C=1|
|8||T(or blank)||Always True(default)||-|
|9||GE||Greater Than or Equal||(S XOR V) = 0|
|A||GT||Greater Than||(Z OR (S XOR V)) = 0|
|B||UGT||Unsigned Greater Than||(C = 0 AND Z = 0) = 1|
|F||UGE||Unsigned Greater Than or Equal||C=0|
main: ;This code will loop infinitely. jp mainJump relative to a label
main: ;This code does the same as the previous code: loop indefinitely. jr mainJump relative to anonymous label
$$: jr $F ;Jump Forward to next $$ label (anonymous label) jr $B ;Jump Back to previous $$ label (anonymous label) $$:Jump to local label
$loop: jp $loop ; Infinite branch to $loop lab?: jp lab? ; Infinite branch to lab? scope ; New local label scope $loop: jp $loop ; Reuse $loop lab?: jp lab? ; Reuse lab?
Notice that you have to use extended addressing to be able to access these registers. They are not in range of standard 8 bit addressing.
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