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From: jlavin@cie.uoregon.edu (Jeff Lavin)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Macro-68 Questions
Keywords: Assembler
Message-ID: <1991May10.084719.14832@ariel.unm.edu>
Date: 10 May 91 08:47:19 GMT
References: <mykes.2256@amiga0.SF-Bay.ORG> <1991May8.205935.26761@unislc.uucp>
Sender: Jeff Lavin
Reply-To: jlavin@cie.UUCP (Jeff Lavin)
Organization: The Puzzle Factory
Lines: 56

In article <1991May8.205935.26761@unislc.uucp> ttobler@unislc.uucp (Trent Tobler) writes:
>From article <mykes.2256@amiga0.SF-Bay.ORG>, by mykes@amiga0.SF-Bay.ORG (Mike Schwartz):
>
>>>2) Is bhs.s the same as bhi.s followed by beq.s?  That is what
>>>   I assumed, bhs is not a true 68000 opcode in any case.
>>>
>> 
>> bhs.s means "branch higher or same" and it IS a true 68000 opcode.  It
>> is an unsigned branch while bge is signed.
>
>No, it is not a true 68000 opcode.  The branching instructions are:
>
>Cond.
>0000  BRA	always
>0001  ---        used for the BSR instruction
>0010  BHI	C and Z clear
>0011  BLS	C or Z set
>0100  BCC	C clear
>0101  BCS	C set
>0110  BNE	Z clear
>0111  BEQ	Z set
>1000  BVC	V clear
>1001  BVS	V set
>1010  BPL	N clear
>1011  BMI	N set
>1100  BGE	N = V (ie both set or both clear)
>1101  BLT	N != B (ie one is set and one is clear)
>1110  BGT	Z clear, and N = V
>1111  BLE	Z set, and N != V
> 
>> These are not anomalies, and you should find these "basic" features in any
>> assembler you consider using.  They were in the oldest Metacomco assembler
>> available...
>
>So what do the assemblers do?  Generate a BHI and BEQ sequence?
>
>-
>   Trent Tobler - ttobler@csulx.weber.edu

Simple, BHS is equivalent to BCC (unsigned).

Because of the user configuration file, Macro68 allows you to rename
all directives and opcodes.  This allows both a large amount of
compatibility with other assemblers, and a lot of flexibility.  Some
folks have reported renaming the signed branches in order to make it
easier for them to remember which are signed and which are unsigned.

Whatever you call it, on the 68K family of processors,
BCC is equivalent to an unsigned Branch Higher or Same, and
BCS is equivalent to an unsigned Branch Lower.


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