Program Assembly Illustration
ASSEMBLY OF DIRECTIVES AND ASM INSTRUCTIONS
Assembly Code Assembled Code (.LST file)
label1 mnemonic2 operand3 prog./data machine opcode5
directive1 mem. addr.4
ORG $6000 =00006000
D_REC FCB $AA,$BB,$CC,$FF,$EE,$01 6000 AA BB CC FF EE 01
FCB $A1,$B2,$C3,$F4,$01 6006 A1 B2 C3 F4 01
FCB $81,$72,$63,$54,$45,$E5,$01 600B 81 72 63 54 45 E5 01
RESULT RMB $0A 6012 +000A
D_CPY RMB $10 601C +0010
ORG $4000 =00004000
LDS #$8000 4000 CF 8000
LDX #D_REC 4003 CE 6000
LDY #D_CPY 4006 CD 601C
LDAA #$0 4009 86 00
PSHA 400B 36
LOOP LDAB 0,X 400C E6 00
STAB 0,Y 400E 6B 40
CMPB #$01 4010 C1 01
BEQ ENDLP 4012 27 05
INX 4014 08
INY 4015 02
INCA 4016 42
BRA LOOP 4017 20 F3
ENDLP PULB 4019 33
PSHY 401A 35
LDY #RESULT 401B CD 6012
STAA B,Y 401E 6A ED
PULY 4020 31
INCB 4021 52
PSHB 4022 37
CPX #RESULT 4023 8E 6012
BEQ DONE 4026 27 05
INX 4028 08
INY 4029 02
CLRA 402A 87
BRA LOOP 402B 20 DF
DONE TBA 402D 18 0F
END
Notes:
1. Labels and Directives are used by the assembler to simplify writing code and direct the assembly
process. During assembly, all labels are replaced with appropriate hexadecimal values. Directives do
not result in any program opcodes, although they can generate data to be stored in memory.
2. Mnemonics are shorthand names for assembly instructions. Mnemonics will be converted to
hexadecimal opcodes (machine code) during the assembly process that are loaded into
microcontroller program memory to form the program that can be executed.
3. Operands are the data parameters needed to complete a program instruction or assembly directive
statement. Hexadecimal operands must be begin with a ‘$’ so the assembler knows the value is not a
decimal. The address mode for instructions is determined by the format of the operand; e.g., ‘#’
specifies an immediate instruction where the operand is the parameter value not an address
containing the parameter value. Multiple operands can be separated by comma or tabs, depending
on the assembler used to assemble the code.
