1- 8 M68020 USER’S MANUAL MOTOROLA
1.3 DATA TYPES AND ADDRESSING MODES OVERVIEW
For detailed information on the data types and addressing modes supported by the
MC68020/EC020, refer to M68000PM/AD,
M68000 Family Programmer’s Reference
Manual
.
The MC68020/EC020 supports seven basic data types:
1. Bits
2. Bit Fields (Fields of consecutive bits, 1–32 bits long)
3. BCD Digits (Packed: 2 digits/byte, Unpacked: 1 digit/byte)
4. Byte Integers (8 bits)
5. Word Integers (16 bits)
6. Long-Word Integers (32 bits)
7. Quad-Word Integers (64 bits)
In addition, the MC68020/EC020 instruction set supports operations on other data types
such as memory addresses. The coprocessor mechanism allows direct support of floating-
point operations with the MC68881 and MC68882 floating-point coprocessors as well as
specialized user-defined data types and functions.
The 18 addressing modes listed in Table 1-1 include nine basic types:
1. Register Direct
2. Register Indirect
3. Register Indirect with Index
4. Memory Indirect
5. PC Indirect with Displacement
6. PC Indirect with Index
7. PC Memory Indirect
8. Absolute
9. Immediate
The register indirect addressing modes have postincrement, predecrement, displacement,
and index capabilities. The PC modes have index and offset capabilities. Both modes are
extended to provide indirect reference through memory. In addition to these addressing
modes, many instructions implicitly specify the use of the CCR, stack pointer, and/or PC.
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