25
votes
Accepted
Which undocumented 8085 instructions is Steven Morse referring to in "In The Beginning"?
Ken Shirriff has, as so often, a nice table to start with - especially nice to detect the 'undocumented' ones. All opcodes in lower case are 'undocumented'. With sorting his table according to the '...
- 208k
24
votes
Accepted
Z80 to x86 asm translator?
I'm going to say "No" simply because the 8086 doesn't support the alternate registers of the Z80. That was a fairly important concept that you can not directly mimic on the 8086.
Mind, if ...
- 12.1k
14
votes
Z80 to x86 asm translator?
Sure, a lot can be done. Source code translation always offers the possibility to replace one instruction by a sequence - like Intel already did for a few. This would as well solve the issue of ...
- 208k
12
votes
Accepted
8080/8085 Instruction Test Suite
I've found three programs which together make up quite a comprehensive test suite.
8080/8085 CPU Diagnostic, version 1.0, by Microcosm Associates
Diagnostics II, version 1.2, CPU test by Supersoft ...
- 9,392
11
votes
Accepted
Intel 8080 Read/Set Interrupt Mask Instructions
The 8085 added two new instruction functions: SIM and RIM.
These instructions differ from the 8080 instructions in that each has multiple functions. The SIM instruction sets the interrupt mask and ...
- 9,392
10
votes
Simulating a 8085 using a Z80?
my goal is to be able to be compatible with hardware and software
targetted at the old system.
Would it be feasible?
Depends on the architecture of the target system and how compatible you want to be....
- 6,615
9
votes
How much extra die area did a CMOS CPU take?
If you had parity equipment and nodes, the CMOS implementation would be physically smaller. The "weak pull up" was created by having "n" diffusion implant into your "p+" ...
- 1,059
9
votes
Accepted
Why did the 8085 multiplex data with the low address byte?
The reason is already within your question when looking at
... like the 8185, 8355, 8755, ...
and
So you could have up to 256 bytes of ROM and some I/O peripherals, and still make a very useful ...
- 208k
8
votes
Accepted
Carry flag in 8080/8085 subtraction
The 8080 sets the carry flag when the unsigned value subtracted is greater than the unsigned value it is subtracted from. So for SUB B carry is set if and only if the unsigned value of B register is ...
- 7,636
6
votes
Intel 8080 Read/Set Interrupt Mask Instructions
To answer your specific question, the 0x20 and 0x30 opcodes on the 8080 were undefined. In practice they were equivalent to NOP (0x00).
A handy table of 8080 instructions can be found here:
http://...
- 7,636
6
votes
Simulating a 8085 using a Z80?
There are a bunch of problems you hit having gone the other way with an 8085 CPU board for a Z80 designed hardware bus.
As well as RIM and SIM there are a bunch of originally undocumented 8085 ...
- 991
4
votes
Z80 to x86 asm translator?
First, note that although Intel claimed 8080-to-8086 asm source compatibility, their CONV86 was slow, cranky, and produced bloated code that often had outright errors. Converting from Z80 asm ...
- 49
3
votes
Accepted
Netronics Explorer 85 level A interrupt handling mechanism
TL;DR:
During Reset and Interrupt handling the ROM is accessed for one instruction fetch instead of RAM (*1)
The Explorer/85 is, as it's schematic show, a very BASIC 8085 system using the full ...
- 208k
3
votes
How much extra die area did a CMOS CPU take?
The size ratio between equivalent "conventional" NMOS and CMOS designs varies with the feature size. If feature sizes of an NMOS design are cut in half, the amount of power each passive ...
- 34k
3
votes
Accepted
How much extra die area did a CMOS CPU take?
CMOS requires 2N MOSFETs for every N inputs. NMOS requires (N+1) MOSFETs for every N inputs. This is why the CMOS versions of common micros, like the 65C02, have roughly double the number of ...
- 19.1k
2
votes
Accepted
Execution time for conditional jumps on the Intel 8080
I'm not really clear what the underlaying problem/question is, as you already cite all relevant information to answer waht seams to be the question. Thus it's hard to give a straight answer, meaning I ...
- 208k
Only top scored, non community-wiki answers of a minimum length are eligible