For some instructions there are two valid mnemonics for the same op-code, or there is
more than one assembly language equivalent. The disassembler may choose a form
different from the one originally entered. For example:
BRA is returned for BT
DBF is returned for DBRA
The assembler recognises two forms of mnemonic for two branch instructions. The BT
form (branch conditional always true) has the same op-code as the BRA instruction.
DBRA (decrement and branch always) and DBF (never true, decrement, and branch)
mnemonics are different forms for the same instruction. The assembler will accept
both forms.
Mnemonics and Delimiters
The assembler recognises MC68000 instruction mnemonics. Numbers are recognised as
both decimal and hexadecimal with decimal being the default (Note, this is the reverse
of the monitor commands).
One or more ASCII characters enclosed by apostrophes (’) constitute an ASCII string.
ASCII strings are left justified and zero filled (if necessary), whether stored or used as
immediate operands. Left justification will be to a word boundary if one or two
characters are specified; or to a long word boundary if the string contains more than two
characters:
DC.W
’S’
MOVE.L
# ’ABCD’,D1
DC.W
’56’
The following register mnemonics are recognised by the assembler:
D0-D7 Data
Registers
A0-A7 Address
Registers
A7, SP
Either mnemonic represents the system stack pointer of the active system
state.
USP
User Stack Pointer. Used only in privileged instructions which are restricted
to the supervisory state.
CCR
Condition Code Register (lower 8 bits of SR)
SR
Status Register. All 16 bits may be modified in the supervisor state.
Only the lower 8 bits (CCR) may be modified in the user state.
PC
Program Counter. Used only in program counter relative addressing.
PME68-1B Manual
Page 109 Issue 5
Содержание PME 68-1B
Страница 8: ...Figure 1 The PME 68 1B Board Photograph not available in PDF PME 68 1B Manual Page 2 Issue 5...
Страница 12: ...Figure 4 Component Layout Diagram P5 P4 P3 BAT PME 68 1B Manual Page 6 Issue 5...
Страница 56: ...Figure 14 Link Areas BAT PME68 1B Manual Page 50 Issue 5...
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Страница 59: ...Figure 15 Location of System EPROM Area 1 2 3 4 1 2 3 4 WC1 WC2 PME68 1B Manual Page 53 Issue 5...
Страница 80: ...Figure 41 Location of BERR Jumpers 1 2 3 4 WK1 WK2 BR26 2 3 1 BAT PME68 1B Manual Page 74 Issue 5...
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