Unknown 8085 opcodes

[Hayden Kroepfl]

Another possibility could be self-modifying mode, something somewhere else
could be writing over this code once it's running. Though that would be
assuming it's in RAM. Though the code around these instructions seems
confusing. Looking at the values it almost looks like it's ASCII text and
not actual code data. I see numbers in the 0x40 and 0x60 range which are
the ASCII lowercase and uppercase letters. Along with 0x20 which is a
space. Perhaps try interpreting the data as data instead of code?

On Wed, Jan 11, 2017 at 10:10 AM, Adrian Graham <binarydinosaurs at gmail.com>
wrote:

> Hi folks,
>
> Any 8085 assembler geeks in the house?
>
> Official Intel docs don't seem to be helping with this one, I have 8085 and
> D8741A peripheral controller dumps both containing several opcodes that two
> disassemblers aren't recognising and any docs I've been looking through for
> either 8085 instructions or the UPI instruction set don't seem to feature
> them either.
>
> The codes are 0x08, 0x10, 0x18, 0x28, 0x38,0xD9, 0xDD and 0xED.
>
> 0x08 nearly always follows a 0x01 LXI B instruction, the others don't seem
> to have an obvious pattern.
>
> I've pondered if 0x10 is INC @R0 because the binary for that is 0001 000x
> where x is either 0 or 1.
> By the same reasoning 0xD9 could be XRL A,R1 (opcode 11011xxx) and 0xDD
> could be XRL A,R5 but can't match the others. Also the surrounding code
> doesn't mention those registers.
>
> Example 8085 code fragment:
>
> 3440   1792 09                  DAD B
> 3441   1793 01 01 08            LXI B,0801H
> 3442   1796 08                  UNRECOGNIZED
> 3443   1797 12                  STAX D
> 3444   1798 0D                  DCR C
> 3445   1799 54                  MOV D,H
> 3446   179A 65                  MOV H,L
> 3447   179B 6C                  MOV L,H
> 3448   179C 65                  MOV H,L
> 3449   179D 70                  MOV M,B
> 3450   179E 68                  MOV L,B
> 3451   179F 6F                  MOV L,A
> 3452   17A0 6E                  MOV L,M
> 3453   17A1 65                  MOV H,L
> 3454   17A2 20                  RIM
> 3455   17A3 44                  MOV B,H
> 3456   17A4 65                  MOV H,L
> 3457   17A5 74                  MOV M,H
> 3458   17A6 61                  MOV H,C
> 3459   17A7 69                  MOV L,C
> 3460   17A8 6C                  MOV L,H
> 3461   17A9 73                  MOV M,E
> 3462   17AA 01 04 05            LXI B,0504H
> 3463   17AD 08                  UNRECOGNIZED
> 3464   17AE 17                  RAL
> 3465   17AF 53                  MOV D,E
> 3466   17B0 65                  MOV H,L
> 3467   17B1 6C                  MOV L,H
> 3468   17B2 65                  MOV H,L
> 3469   17B3 63                  MOV H,E
> 3470   17B4 74                  MOV M,H
> 3471   17B5 20                  RIM
>
> Cheers!
>
> --
> adrian/witchy
> Owner of Binary Dinosaurs, the UK's biggest home computer collection?
> www.binarydinosaurs.co.uk
>