koleman@pnet51.orb.mn.org (Kurt "Koleman" Koller) (04/12/91)
Ok, I was looking at some source in Assembly, and I saw some instructions that
I wasn't familiar with. My assembler (Macro 68) assembles them just fine, and
they ARE mentioned in the 68000 manual, but just MENTIONED. I have no idea
what they do. If anyone can help me, so be it.
st (MemoryLocation)
sne d(n)
sf
sge
etc...
These are not "documented" instructions. What do they do, and why would
someone use them other than to save cycles or 10? Are they also used on the
020 030 040 etc?
Thanks,
--------------------------- _ _ _ _ ___ __ __ _ __ _
| Kurt "Koleman" Koller | ( )/ ) /,\ ( ) ( __)( \/ ) ( ) ( \ ( )
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INET: koleman@pnet51.orb.mn.orgccplumb@rose.waterloo.edu (Colin Plumb) (04/12/91)
koleman@pnet51.orb.mn.org (Kurt "Koleman" Koller) wrote: > Ok, I was looking at some source in Assembly, and I saw some instructions > that I wasn't familiar with. My assembler (Macro 68) assembles them just > fine, and they ARE mentioned in the 68000 manual, but just MENTIONED. I > have no idea what they do. If anyone can help me, so be it. > st (MemoryLocation) > sne d(n) > sf > sge > These are not "documented" instructions. What do they do, and why would > someone use them other than to save cycles or 10? Are they also used on the > 020 030 040 etc? These are the "set conditional" instructions, which are documented under "Scc" like all the branches are collectively called "Bcc". If the condition is true ("t" is always true, "f" never is), they set the destination byte to all 1's, otherwise they clear it to all 0's. Obviously, their function can be emulated with other instruction sequences (conditional branches are easiest), but that's true of most 68000 instructions. -- -Colin
dillon@overload.Berkeley.CA.US (Matthew Dillon) (04/13/91)
In article <4577@orbit.cts.com> koleman@pnet51.orb.mn.org (Kurt "Koleman" Koller) writes: > >Ok, I was looking at some source in Assembly, and I saw some instructions that >I wasn't familiar with. My assembler (Macro 68) assembles them just fine, and >they ARE mentioned in the 68000 manual, but just MENTIONED. I have no idea >what they do. If anyone can help me, so be it. > > st (MemoryLocation) > sne d(n) > sf > sge > >etc... > > These are not "documented" instructions. What do they do, and why would >someone use them other than to save cycles or 10? Are they also used on the >020 030 040 etc? They're magik, of course! Actually, they are individual branch codes for the Scc instruction (set according to condition). The format is: Scc.b <ea> Scc is always a byte operation. If the specified condition is TRUE, the byte destination is set to all 1's (-1). If it is FALSE, the byte destination is set to all 0's. The 'cc' follows the DBcc branch codes which is the same as the Bcc branch codes except for the 't' and 'f' code (always true and always fast). st D0 (always true), sets lower byte of D0 to 1's sne D0 If not equal ... sf D0 (always false), clears lower byte of D0 sge D0 If greater or equal then.. You can get 0, 1 longword results by following the Scc with a NEG instruction, like this (for example): moveq.l #0,D0 . cmp ... . sne.b D0 neg.b D0 >Thanks, > >--------------------------- _ _ _ _ ___ __ __ _ __ _ >| Kurt "Koleman" Koller | ( )/ ) /,\ ( ) ( __)( \/ ) ( ) ( \ ( ) >| P.O. Box 50656 | ( \ ( )( )__ ( __)( )\/( ) (_|_) ( )\\( ) >| Mendota, MN 55150-0656 | (_)\_) \_/ (____)(___)(_) (_)(_) ( )(_) \__) >--------------------------- >UUCP: {crash tcnet}!orbit!pnet51!koleman >INET: koleman@pnet51.orb.mn.org -Matt -- Matthew Dillon dillon@Overload.Berkeley.CA.US 891 Regal Rd. uunet.uu.net!overload!dillon Berkeley, Ca. 94708 USA
conan@ccwf.cc.utexas.edu (Robert Faulkner) (04/13/91)
>From: koleman@pnet51.orb.mn.org (Kurt "Koleman" Koller) >Ok, I was looking at some source in Assembly, and I saw some instructions that >I wasn't familiar with. My assembler (Macro 68) assembles them just fine, and >they ARE mentioned in the 68000 manual, but just MENTIONED. I have no idea >what they do. If anyone can help me, so be it. > > st (MemoryLocation) > sne d(n) > sf > sge >etc... > > These are not "documented" instructions. What do they do, and why would >someone use them other than to save cycles or 10? Are they also used on the >020 030 040 etc? These are Set According to Condition commands in the form Scc <ea> The specified condition code is Tested, if the condition is true, the byte specified by the effective address is set to TRUE, (all ones), otherwise that byte is set to False (all zeroes), "CC" may specify the following conditions CC Carry Clear LS Low or Same CS Carry Set LT Less Than EQ Equal MI Minus F False NE Not Equal GE Greater or Equal PI Plus GT Greater Than T True HI High VC Overflow Clear LE Less or Equal VS OverFlow Set This command is a good way to set a Boolean Flag byte in a return value for a function. As far as I know it is supported on all of the 680x0 processors. Feel free to e-mail me with any other questions. I got all of this information from the S68000 User's Guide, which only costs about $0.65 at our University Book Store. You can also call Signetics and they will send you one free, plus a bunch of other useful information on the 68000. The phone # is 408-739-7700, ask for publications department. Thanks, -- Robert Faulkner conan@ccwf.cc.utexas.edu /// Recursion: Thinking \\\/// University of Texas about \\// Amiga Computers Thinking
knurlin@spf.trw.com (Scott Karlin) (04/13/91)
In article <4577@orbit.cts.com> koleman@pnet51.orb.mn.org (Kurt "Koleman" Koller) writes: > >Ok, I was looking at some source in Assembly, and I saw some instructions that >I wasn't familiar with. My assembler (Macro 68) assembles them just fine, and >they ARE mentioned in the 68000 manual, but just MENTIONED. I have no idea >what they do. If anyone can help me, so be it. > > st (MemoryLocation) > sne d(n) > sf > sge These are examples of the Scc (Set According to Condition) instructions. If the condition specified by "cc" is true then the byte operand is set to all bits 1, otherwise all bits 0. The conditions specified by your four examples are: always true, not equal, never true, & greater or equal. This information can be found in the "8-/16-/32-Bit Microprocessors User's Manual" ISBN: 0-13-567074-8. -- Scott Karlin knurlin@spf.trw.com -- TRW Data Systems Center Phone: (213) 812-7335 -- One Space Park, O2-1761 -- Redondo Beach, CA 90278-1071
sschaem@starnet.uucp (Stephan Schaem) (04/14/91)
Speaking of Scc, a good way to use it is to set the bliter minterm with it... For plane Set/Clear. If you have a color value (x fliped:-) just do an add.b dx,dx and SCC dy. Could be use for seting byte flag (using Scc and Tst). SF can be used instead of clr.b ... (but same timing, but slower on a 68020) Anyway, you sould get the Programer's Reference Manual. Stephan.
umueller@iiic.ethz.ch (Urban Dominik Mueller) (04/16/91)
To all programmers: This is a call for submissions to the WHO'S WHO OF
COMP.SYS.AMIGA. Whoever has published anything on the Amiga or has some
special knowledge others might be interested in should be mentioned. So if
you'd like yourself or someone else included, please submit the address in
the following format:
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71545.1466@compuserve.com Jeff Davis R:Manx technical support
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dillon@Overload.Berkeley.CA.US Matt Dillon A:DICE, DMouse, DNet, UUCP
fishpond!fnf@phx.mcd.mot.com Fred Fish R:Fish disks
jesup@cbmvax.cbm.commodore.com Randell Jesup R:C= AmigaDOS
umueller@iiic.ethz.ch Urban Mueller A:csh, who's who K:Aztec C 5.0d
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| "Don't tell my employer" | \__/ | SWITZERLAND |koleman@pnet51.orb.mn.org (Kurt "Koleman" Koller) (04/17/91)
sschaem@starnet.uucp (Stephan Schaem) writes: >Speaking of Scc, a good way to use it is to set the bliter minterm with >it... For plane Set/Clear. >If you have a color value (x fliped:-) just do an add.b dx,dx and SCC >dy. >Could be use for seting byte flag (using Scc and Tst). >SF can be used instead of clr.b ... >(but same timing, but slower on a 68020) >Anyway, you sould get the Programer's Reference Manual. > > Stephan. Just to save face here... The reason that I posted this inquiry is because I have 3 books here, one of which is a Motorola reference on the 68000, none of which have any set instructions under the heading Scc or any other similar heading. That is why I asked here. I AM literate. --------------------------- _ _ _ _ ___ __ __ _ __ _ | Kurt "Koleman" Koller | ( )/ ) /,\ ( ) ( __)( \/ ) ( ) ( \ ( ) | P.O. Box 50656 | ( \ ( )( )__ ( __)( )\/( ) (_|_) ( )\\( ) | Mendota, MN 55150-0656 | (_)\_) \_/ (____)(___)(_) (_)(_) ( )(_) \__) --------------------------- UUCP: {crash tcnet}!orbit!pnet51!koleman INET: koleman@pnet51.orb.mn.org