Unknows S-100 System

[Allison]

>
>Subject: Re: Unknows S-100 System
>   From: "Roy J. Tellason" <rtellason at verizon.net>
>   Date: Sun, 23 Sep 2007 12:35:38 -0400
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>

snippage>>>>>>>>>

>> What irritated me was that Intel never documented the additional 8085
>> instructions, even though they seemed to be present on every version
>> of the chip Intel (and second sources) ever produced.  Because they
>> weren't "officially" documented, we adopted a policy that they should
>> not be used to avoid possible future "surprises".
>
>What are these?  I remember some stuff in the magazines early on (probably 
>Byte,  in its first year of publication or so) and have run across some stuff 
>on the 'net about undocumented z80 opcodes,  most of which don't seem to be 
>terribly useful,  but this is the first I've heard of undocumented 8085 
>codes.

from my compendium of acient history and useful junk:

Hex   8085 Meaning
---------------------
08	SUB HL-BC

10	RRHL	   ;Rotate HL right. 16-bit rotation, flags unchanged.
10	Shift right HL

18	RLDE	   Rotate DE left. Bit 15 to Carry. No other flags.
18	Rotate right DE

28bb	ADI HL,bb  ;Add 00bb immediate to HL, setting flags.
28	Add     HL and Immidiate nnnn into DE

38bb	ADI SP,bb  ;As above but to Stack Pointer.
38	Add SP and Immidiate nnnn into DE

CB	RSTV8	   ;RST 8 (to 0040) if the V flag is set.
CB	ReSTart on Overflow(V) to 0040h

D9	SHLDE	   ;LD (DE),HL
D9	Load [DE] from HL

DDaaaa	JNK aaaa   ;Jump to location aaaa if K flag is reset.
DD	Jump on 'Not X5'

ED	LHLDE	   ;LD HL,(DE)
ED	Load Hl from [DE]

FDaaaa	JK aaaa    ;Jump to location aaaa if K flag is set.
FD	Jump on 'X5'


bit 	8085
7(MSB)  S 	sign
6 	Z 	Zero
5 	X5 	
4 	AC 	aux carry
3 	0 	
2 	P 	parity
1 	V 	overflow
0(LSB)  C 	carry

Intel did not further specify the undocumented 8085 instructions. 
This however means that other assemblers might use different mnemonics for the same function. 

DSUB        08         10cy   HL <- HL - BC
Instruction : DSUB [reg] (DSB BC)
Function    : HL HL - reg (double subtract)
Flags       : CY, S, X5, AC, Z, V, P 
Arguments   : reg = B for BC (optional) 

ARHL        10          7cy   HL <- HL/2, CY <- L0
Instruction : ARHL (SHRL)
Function    : HL,CY HL >> 1 (arithmetc right shift) 
Flags       : CY 
Argument    : none 

RDEL        18         10cy   DE <- DE*2, E0 <- CY, CY <- D7
Instruction : RDEL (SLDE) 
Function    : CY,DE DE << 1  (arithmetic right shift)
Flags       : CY, V 
Arguments   : none 

LDHI  imm   28 dd      10cy   DE <- HL + imm
Instruction : LDHI d8 (LRI HL,D8)
Function    : DE HL + d8  (HL + 8bit >DE)
Flags       : none 
Arguments   : d8 = 8-bit constant 

LDSI  imm   38 dd      10cy   DE <- SP + imm
Instruction : LDSI d8 (LRI SP,D8)
Function    : DE SP + d8 (SP+ D8 >DE
Flags       : none 
Arguments   : d8 = 8-bit constant 

RSTV        CB        6/12cy  if(V) push PC, PC <- 40H
Instruction : RST flag (RSTV)
Function    : restart to 40h if flag=1 
Flags       : none 
Arguments   : flag = V 

SHLX        D9         10cy   (DE) <- HL
Instruction : SHLX DE 
Function    : DE < [HL] 
Flags       : none 
Arguments   : reg = DE

LHLX        ED         10cy   HL <- (DE)
Instruction : LHLX DE 
Function    : [DE] > HL 
Flags       : none 
Arguments   : reg =  DE

JNX5  addr  DD al ah  7/10cy  if(!X5) PC <- addr
Instruction : JNX5 addr 
Function    : jump to addr if X5=0 
Flags       : none 
Arguments   : addr = absolute 16-bit address 

JX5   addr  FD al ah  7/10cy  if(X5) PC <- addr
Instruction : JX5 addr 
Function    : jump to addr if X5=1 
Flags       : none 
Arguments   : addr = absolute 16-bit address 

X5 is the otherwise unused bit 5 in the PSW register


Allison