Msg: 7082 *Conference*

04-09-97 18:05:41

From: RON WIESEN

To : COMET _

Subj: REPLY TO MSG #7074 (UNDOCUMENTED 80C85 OPCODES)

Your MSG_7090 regarding undocumented 80C85 opcodes is below with my corrections
and additions.  The "**" tag I recognize from Pages 23 and 24 of the ROM2 v5.1
user manual from Polar Engineering, fourth printing September 1, 1985.
However, the mnemonics look like something born of the 8080.  Wonder what
source these mnemonics came from Comet? I've listed the mnemonics with respect
to ROM2.  Also, the last item "RSTV" (CB hexidecimal) doesn't appear in the
manual - more on this later.
 
There are three opcodes where the hexidecimal value is incorrect due to 
confusing "B" with "8" and vica-versa.  I put a "?" beside these and show the
correct value in a following line.
 
___________________________________________________________________|_MNEMON IC_
\** unspecified 8085 op codes:
> (hl)= (hl) - (bc)                           DSUB          08    1  HLMBC
> shift (hl) right; msb unchanged; (cy) = lsb ARHL          10    1  SHLR
> rotate (de) left through carry              RDEL          1B?   1 CORRECTION
18       RDEL
 
> (de)= (hl) + *                              LDHI *        2B?   2 CORRECTION
28       DEHL byte
> (de)= (sp) + *                              LDSI *        38    2  DESP byte
 
> (l)= ((de)); (h)= ((de)+1)                  LHLX          ED    1  LHLI
> ((de))= (l); ((de)+1)= (h)                  SHLX          D9    1  SHLI
 
> if x5==1: jmp *                             JX5  *        FD    3  JTM label
> if x5==0: jmp *                             JNX5 *        DD    3  JTP label
> if overflow (v): call 40H                   RSTV          C8?   1 CORRECTION
CB       unknown
___________________________________________________________________|_______ ___
 
Attached is file OP8085.DO which lists the 8085 instructions in three tables:
Mnemonic Meanings by Functional Group, Actions by Functional Group, and by
Mnemonic (alpha sorted).  The mnemonics with syntax for assembly are as defined
for the ROM2 assembler.  Print it and insert it after page 22 of the ROM2 user
manual.
 
As for RSTV, nowhere in any of my sources do I find it.  As far as it equating
to an RST 8 which would call address 40H, in the Model T this is non-sensical
because address 40H in the standard ROM is the beginning of a vector table for
functions SGN to MID$.  Consequently, these 16-bit vectors are not intended to
be "fetched" as executible code.  If the 8085 has such an instruction, then
it's not germane to the Model T.  Again I wonder, what source did you get this
from?

*Enclosed File: OP8085.DO