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able) as well as the following condition codes: overflow (V), zero (Z), negative
(N), carry (C), and extend (X). Additional status bits indicate that the processor
is in trace (T) mode and/or in a supervisor (S) state.
2.2 INSTRUCTION SET SUMMARY
2-4
The five data types supported are bits, binary-coded decimal (BCD) digits (4
bits), bytes (8 bits), words (16 bits), and long words (32 bits).
In addition, operations on other data types, such as memory addresses, status
word data, etc., are provided for in the instruction set. Shown in Table 2-1,
the 14 flexible addressing modes include six basic types:
• Register Direct
• Register Indirect
• Absolute
• Immediate
• Program Counter Relative
• Implied
The capability to perform postincrementing, predecrementing, offsetting, and
indexing is included in the register indirect addressing modes. Program
counter relative modes can also be modified via indexing and offsetting.
The M68000 instruction set is shown in Table 2-2.
Some basic instructions also have variations as shown in Table 2-3.
Special emphasis has been placed on the instruction set to simplify pro-
gramming and to support structured high-level languages. With a few ex-
ceptions, each instruction operates on bytes, words, or long words, and most
instructions can use any of the 14 addressing modes.
Combining instruction types, data types, and addressing modes provides
over 1000 useful instructions. These instructions include signed and unsigned
multiply and divide, quick arithmetic operations, BCD arithmetic, and ex-
panded operations (through traps).
MC68302 USER'S MANUAL
MOTOROLA
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