Data Organization And Addressing Capabilities; Instruction Operands - Motorola MC68030 User Manual

SECTION 2
DATA ORGANIZATION AND ADDRESSING
CAPABILITIES
Most external references to memory by a microprocessor are either program
references or data references; they either access instruction words or op-
erands (data items) for an instruction. Program references are references to
the program space, the section of memory that contains the program in-
structions and any immediate data operands that reside in the instruction
stream. Refer to M68000PM/AD, M68000 Programmer's Reference Manual,
for descriptions of the instructions in the program space. Data references
refer to the data space, the section of memory that contains the program
data. Data items in the instruction stream can be accessed with the program
counter relative addressing modes, and these accesses are classified as pro-
gram references. A third type of external reference used for coprocessor
communications, interrupt acknowledge cycles, and breakpoint acknowledge
cycles is classified as a CPU space reference. The MC68030 automatically
sets the function codes to access the program space, the data space, or the
CPU space for special functions as required. The function codes can be used
by the memory management unit to organize separate program (read only)
and data (read-write) memory areas.
This section describes the data organization and addressing capabilities of
the MC68030. It lists the types of operands used by instructions and describes
the registers and their use as operands. Next, the section describes the or-
ganization of data in memory and the addressing modes available to access
data in memory. Last, the section describes the system stack and user pro-
gram stacks and queues.
2.1 INSTRUCTION OPERANDS
The MC68030 supports a general-purpose set of operands to serve the re-
quirements of a large range of applications. Operands of MC68030 instruc-
tions may reside in registers, in memory, or within the instructions themselves.
An instruction operand might also reside in a coprocessor. An operand may
be a single bit, a bit field of from 1 to 32 bits in length, a byte (8 bits), a word
(16 bits), a long word (32 bits), or a quad word (64 bits). The operand size
for each instruction is either explicitly encoded in the instruction or implicitly
MOTOROLA MC68030 USER'S MANUAL
2-1