6800 Emulator

About

6800IDE is a freeware windows based IDE for Motorola's 6800/6811 processor. Designed for educational purposes, it includes an assembler and an emulator for the 6800/6811 with builtin debugging support such as user breakpoints, execution trace, internal register display and a Hex/Bin/Dec number convertor.

The 6800/6811 family of processors fueled the early home computing explosion and its derivatives were the processors of choice for many personal computers including Apple, Commodore64, Nintendo etc, and numerous gaming consoles. Its direct decendents are still widely used today as embedded processors.

The 6800/6811 is an 8 bit, dual accumulator processor with flexible memory addressing modes. Compared to other processors, it's compact, and highly orthogonal instruction set makes it easier to program.

Screen Shots

Development / Debug Mode

Output Display Mode

Programming Reference

Specifications

Memory Mapped IO Support

Data Input Ports

Keyboard data at port $FFF0,1
Mouse cursor X coordinate at port $FFF2
Mouse cursor Y coordinate at port $FFF3

Data Output

Display Buffer at $FB00 to $FF38
20 lines of 54 characters

Interrupt Vectors

_RST @ 0xFFFE,F
NMI @ 0xFFFC,D
SWI @ 0xFFFA,B
IRQ @ 0xFFF8,9

Execution Trace Support:

Current Program line Highlight
Current Memory Location Highlight

User Break point support:

Disabled
Program Line No.
PC Address value
SP Address value
X Register value
Accumulator A value
Accumulator B value
Memory location changed value

Number Base Conversion:

Hexadecimal <=> Decimal
Hexadecimal <=> Binary
Decimal <=> Binary

Introductory Tutorial

6800.pdf [Adobe Acrobat PDF - 604.55 KB]

Programming Reference

Assembly statements contain the following fields: [Label] Operation [operand] [comment]

Label: Can be used to define a symbol, to skip the field use a blank or tab
Operation: Defines the opcode or directive. (Not case sensitive)
Operand: Contains an address or the data for the instruction. (Ignored with inherent addressing)
Comment: Used for software documentation can be at end or start of statement.; Uses a semicolon to start the comment.
Examples: label adda 3 ; comment here
adda label
clra ; inherent address
; this is a full line comment

Assembler Directives

Tag	Description	Example
.org	Where to put code	.org $200
.equ	Define Constant	.equ 100
.setw	Preset memory word	.setw $FFFE,10
.rmb	Reserve Memory	.rmb 16
.byte	Define Variable	.byte 64
.byte	Array of bytes	.byte 1,2,3
.word	Define Variable	.word 5000
.word	Array of words	.word 1,2,3
.str	Define string	.str "text"
.end	End of Program	.end

Number Formats

Prefix	Description	Example
	Decimal	320
$	Hex	$240
%	Binary	%0110101
'	Character	'm

Operand Formats

Format	Description	Examples	Mode
	Inherent	CLRA	H
#<data>	Immediate	LDDA #4	I
<data>	Relative	BRA 10	R
<data>	Direct	LDDA 4	D
<data>	Extended	LDDA label	E
<data>,X	Indexed	LDDA 4,X	X

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Instruction Reference

====================================================

Status Flags

- unchanged
* updated
1 set
0 reset

H  I  N  Z  V  C
|  |  |  |  |  |
|  |  |  |  |  --- Carry-Borrow
|  |  |  |  ------ Overflow
|  |  |  --------- Zero
|  |  ------------ Negative
|  --------------- Interrupt Mask
------------------ Half Carry

Mnemonic	Operation	Mode	Status
6800 Undocmented Instructions			HINZVC
HCF	Halt and Catch Fire	H	------
NBA	AND Accumulators [A <= A & B]	H	---**-
	Immediate Versions of STAA STAB STS etc		------
6811 Specific Instructructions			HINZVC
IDIV	Integer Divide 16 x 16	H	---***
FDIV	Factional Divide 16x 16	H	---0
MUL	16 multiply A x B	H	------
DEY	Decrement index reg Y	H	---*--
INY	increment index reg Y	H	---*--
STY	Store Index reg. Y	IDXE	--**0-
STD	Store composite reg. D	IDXE	--**0-
LDY	Load index reg. Y	IDXE	--**0-
LDD	Load composite reg. D	IDXE	--**0-
CPY	compare index reg. Y	IDXE	--****
CPD	compare composite reg. D	IDXE	--****
ABX	Add acc.B to index reg.X	H	------
ABY	Add acc.B to index reg.Y	H	------
PSHX	push index reg.X onto stack	H	------
PSHY	push index reg.Y onto stack	H	------
PULX	pull index reg.X from stack	H	------
PULY	pull index reg.Y from stack	H	------
XGDX	exchange composite reg.D with X	H	------
XGDY	exchange composite reg.D with Y	H	------
TSY	Transfer SP to index reg.Y	H	------
TYS	Transfer index reg.Y to SP	H	------
ADDD	add using composite reg. D	IDXE	--****
LSRD	logical shift right composite reg.D	H	--0***
ASLD	arith. shift left composite reg.D	H	--****
Miscellaneous			HINZVC
NOP	No Operation	H	------
RTI	Return from Interrupt [*not supported]	H	******
RTS	Return from Subroutine	H	------
SWI	Software Interrupt [*not supported]	H	-1----
WAI	Wait for Interrupt	H	-1----
Status Flags			HINZVC
CLC	Clear Carry	H	-----0
CLV	Clear Overflow	H	----0-
CLI	Clear Interrupt Mask	H	-0----
SEC	Set Carry	H	-----1
SEV	Set Overflow	H	----1-
SEI	Set Interrupt Mask	H	-1----
TAP	Set Status Mask [Flags<-AccA]	H	******
TPA	Load Status Flags [AccA<-Flags]	H	------
Branch and Jump			HINZVC
BRA	Branch Always	R	------
BCS	Branch if Carry Set [C=1]	R	------
BCC	Branch if Carry Clear [C=0]	R	------
BMI	Branch if Minus [N=1]	R	------
BPL	Branch if Plus [N=0]	R	------
BVS	Branch if Overflow Set [V=1]	R	------
BVC	Branch if Overflow Clear[V=0]	R	------
BEQ	Branch if Equal [Z=1]	R	------
BNE	Branch if Not Equal [Z=0]	R	------
BLT	Branch if < (signed)	R	------
BLE	Branch if <= (signed)	R	------
BGE	Branch if >= (signed)	R	------
BGT	Branch if > (signed)	R	------
BLS	Branch if Lower or Same (unsgn)	R	------
BHI	Branch if Higher (unsigned)	R	------
BSR	Branch to Subroutine	R	------
JSR	Jump to Subroutine	E,X	------
JMP	Jump Absolute	E,X	------
Stack and Index			HINZVC
CPX	Compare X	IDXE	---*--
DES	Decrement SP [SP <- SP - 1]	H	------
DEX	Decrement X [ X <- X - 1]	H	---*--
INS	Increment SP [SP <- SP + 1]	H	------
INX	Increment X [ X <- X + 1]	H	---*--
LDS	Load SP	IDXE	--**0-
LDX	Load X	IDXE	--**0-
STS	Store SP	DXE	--**0-
STX	Store X	DXE	--**0-
TSX	Transfer SP,X [X <= SP + 1]	H	------
TXS	Transfer X,SP [SP <= X - 1]	H	------
Accumulator Only ==> NEMz can be either NEMA or NEMB <==			HINZVC
ASLz	Arithmetic Shift Left Acc	H	--****
ASRz	Arithmetic Shift Right Acc	H	--****
LSRz	Logical Shift Right Acc	H	--0***
ROLz	Rotate Left Acc	H	--****
RORz	Rotate Right Acc	H	--****
CLRz	Clear Accumulator	H	--0100
COMz	One's Complement	H	--**01
DECz	Decrement Acc [A <- A - 1]	H	--***-
INCz	Increment Acc [A <- A + 1]	H	--***-
NEGz	Negate Acc [A <- 0 - A]	H	--****
PSHz	Push Accumulator	H	------
PULz	Pull/Pop Accumulator	H	------
TSTz	Test Acc [A <- A - 0]	H	--**00
ABA	Add Accumulators [A <- A + B]	H	-***
CBA	Compare Accumulators [A - B]	H	--****
DAA	Decimal Adjust Accumulator [*not supported]	H	--****
SBA	Subtract Accumulators [A<-A-B]	H	--****
TAB	Transfer Accumulator [B <- A]	H	--**0-
TBA	Transfer Accumulator [A <- B]	H	--**0-
Memory Reference ==> NEMz can be either NEMA or NEMB <==			HINZVC
LDAz	Load Accumulator [A <- M]	IDXE	--**0-
STAz	Store Accumulator [M <- A]	DXE	--**0-
ADCz	Add with Carry [A <- A+M+C]	IDXE	-***
ADDz	Add [A <- A+M]	IDXE	-***
SBCz	Subtract w. Carry[A <- A-M-C]	IDXE	--****
SUBz	Subtract [A <- A-M]	IDXE	--****
BITz	Bit Test [Z and M]	IDXE	--**0-
ANDz	Logical AND [A <- A and M]	IDXE	--**0-
EORz	Exclusive OR [A <- A xor M]	IDXE	--**0-
ORAz	Inclusive OR [A <- A or M]	IDXE	--**0-
CMPz	Compare Memory [A - M]	IDXE	--****
ASL	Arithmetic Shift Left	XE	--****
ASR	Arithmetic Shift Right	XE	--****
LSR	Logical Shift Right	XE	--0***
ROL	Rotate Left Memory	XE	--****
ROR	Rotate Right Memory	XE	--****
CLR	Clear Memory [M <- 0]	XE	--0100
COM	Complement Memory[M <- !M]	XE	--**01
DEC	Decrement Memory [M <- M - 1]	XE	--***-
INC	Increment Memory [M <- M + 1]	XE	--***-
NEG	Negate Memory [M <- 0 - M]	XE	--****
TST	Test Memory [M - 0]	XE	--**00

Links

Additional resources on the 6800 can be found: