A simple Python based 8085 assembler.
To clone this repository and assemble the demo file, open a terminal and run:
git clone https://github.com/ept221/8085-Assembler.git
cd 8085-Assembler/src/
python3 assembler.py demo.asm -susage: assembler.py [-h] [-L] [-A] [-B] [-I] [-H] [-C] [-s] [-o OUT] source
A simple 8085 assembler.
positional arguments:
source source file
optional arguments:
-h, --help show this help message and exit
-L, --lineNum include the line number in output
-A, --address include the address in output
-B, --label include the labels in output
-I, --instruction include the instructions and arguments in output
-H, --hex include the hex code in output
-C, --comment include the comments in output
-s, --standard equivalent to -A -B -I -H -C
-o OUT, --out OUT output file name (stdout, if not specified)
The assembler is case insensitive.
Comments begin with semicolons.
MVI A, 0x5C ; This is a comment8 and 16-bit constants are given in hex. 8-bit constants must have two digits, and 16-bit constants must have 4-digits.
MVI A, 0x0C
MVI A, 0C ; The "0x" is optional
MVI A, 7 ; Illegal. 8-bit constants must have two digits
LXI H, 0x03B7
LXI H, 03B7 ; The "0x" is optional
LXI H, 3B7 ; Illegal. 16-bit constants must have four digitsIf an 8-bit constant is given where a 16-bit constant is expected, the 8-bit constant will be converted to a 16-bit constant, with the upper 8-bits all zero.
JNZ 0x3FC7 ; Jump-not-zero to 0x3FC7
JMP FF ; JMP takes a 16-bit argument, but given 8-bits. Will JMP to 0x00FFLabel definitions may be any string ending with a colon, where the string does not match the pattern of an 8 or 16-bit constant.
; Example
;*******************************************************************************
MVI A, 0x5C
Foo: DCR A ; Label definition
JNZ Foo ; Jump-not-zero to Foo
;*******************************************************************************
MVI A, 0x5C
FD: DCR A ; Illegal. Label definition cannot match hex constant format
JNZ FDSets the origin to the given address. Only forward movement of the origin is permitted.
; Example
;*******************************************************************************
MVI A, 55
OUT 42
JMP Start
Start: ORG 0x44
MVI A, 32
OUT 42
;*******************************************************************************
; Assembles to the following:
Address Label Instruction Hex Code
--------------------------------------------------------------------------------
0x0000 MVI A, 55 0x3E
0x0001 0x55
0x0002 OUT 42 0xD3
0x0003 0x42
0x0004 JMP START 0xC3
0x0005 0x44
0x0006 0x00
0x0044 START: MVI A, 32 0x3E
0x0045 0x32
0x0046 OUT 42 0xD3
0x0047 0x42 ; Example
;*******************************************************************************
ORG 0x44
MVI A, C7
OUT 44
ORG 0x00 ; Illegal. Cannot move origin backwards
JMP 0x0044Writes one or more data bytes sequentially into memory.
; Example
;***********************************************************
MVI A, 33
DB 0x44, 0xFE, 0x9C
HLT
;***********************************************************
; Assembles to the following:
Address Instruction Hex Code
------------------------------------------------------------
0x0000 MVI A, 33 0x3E
0x0001 0x33
0x0002 DB 0x44
0x0003 DB 0xFE
0x0004 DB 0x9C
0x0005 HLT 0x76 Equates a symbol with a number.
; Example
;***********************************************************
foo EQU 0xC5F3
MVI A, 33
LXI H, foo
;***********************************************************
; Assembles to the following:
Address Instruction Hex Code
------------------------------------------------------------
0x0000 MVI A, 33 0x3E
0x0001 0x33
0x0002 LXI H, FOO 0x21
0x0003 0xF3
0x0004 0xC5 Defines and reserves the next n-bytes for storage.
; Example
;*******************************************************************************
JMP END
Storage: DS 0x05
LDA Storage
END: OUT 42
;*******************************************************************************
; Assembles to the following:
Address Label Instruction Hex Code
--------------------------------------------------------------------------------
0x0000 JMP END 0xC3
0x0001 0x0B
0x0002 0x00
0x0008 STORAGE: LDA STORAGE 0x3A
0x0009 0x03
0x000A 0x00
0x000B END: OUT 42 0xD3
0x000C 0x42 Anytime an instruction or directive requires a numerical argument, an expression can be used. Supported operations inside expressions include addition and subtraction. The location counter $ is also made available. Expressions may contain symbols, but must resolve within two passes of the assembler, and if used for directive arguments, must resolve in a single pass. All expressions must evaluate to a positive number.
; Example with expression resolution in one pass.
;***********************************************************
foo EQU 10
MVI A, foo - 04
;***********************************************************
; Assembles to the following:
Address Instruction Hex Code
------------------------------------------------------------
0x0000 MVI A, FOO - 04 0x3E
0x0001 0x0C
; Example with expression resolution in two passes.
;***********************************************************
MVI A, foo + 04
foo EQU 30
;***********************************************************
; Assembles to the following:
Address Instruction Hex Code
------------------------------------------------------------
0x0000 MVI A, FOO + 04 0x3E
0x0001 0x34; Example with expression resolution in two passes, and $
;***********************************************************
MVI A, 55
JMP $ + foo
foo equ 05
DB $, $ + 01, $ + foo
DS 02
HLT
;***********************************************************
; Assembles to the following:
Address Instruction Hex Code
------------------------------------------------------------
0x0000 MVI A, 55 0x3E
0x0001 0x55
0x0002 JMP $ + FOO 0xC3
0x0003 0x07
0x0004 0x00
0x0005 DB 0x05
0x0006 DB 0x07
0x0007 DB 0x0C
0x000A HLT 0x76