Datasheet

13.0 Instruction Set
13.1 INTRODUCTION
This section defines the instruction set of the COP8SAx
Family members. It contains information about the in-
struction set features, addressing modes and types.
13.2 INSTRUCTION FEATURES
The strength of the instruction set is based on the follow-
ing features:
•
Mostly single-byte opcode instructions minimize pro-
gram size.
•
One instruction cycle for the majority of single-byte
instructions to minimize program execution time.
•
Many single-byte, multiple function instructions such
as DRSZ.
•
Three memory mapped pointers: two for register indi-
rect addressing, and one for the software stack.
•
Sixteen memory mapped registers that allow an opti-
mized implementation of certain instructions.
•
Ability to set, reset, and test any individual bit in data
memory address space, including the
memory-mapped I/O ports and registers.
•
Register-Indirect LOAD and EXCHANGE instructions
with optional automatic post-incrementing or decre-
menting of the register pointer. This allows for greater
efficiency (both in cycle time and program code) in
loading, walking across and processing fields in data
memory.
•
Unique instructions to optimize program size and
throughput efficiency. Some of these instructions are
DRSZ, IFBNE, DCOR, RETSK, VIS and RRC.
12.3 ADDRESSING MODES
The instruction set offers a variety of methods for speci-
fying memory addresses. Each method is called an ad-
dressing mode. These modes are classified into two cat-
egories: operand addressing modes and
transfer-of-control addressing modes. Operand address-
ing modes are the various methods of specifying an ad-
dress for accessing (reading or writing) data.
Transfer-of-control addressing modes are used in con-
junction with jump instructions to control the execution
sequence of the software program.
13.3.1 Operand Addressing Modes
The operand of an instruction specifies what memory
location is to be affected by that instruction. Several dif-
ferent operand addressing modes are available, allowing
memory locations to be specified in a variety of ways. An
instruction can specify an address directly by supplying
the specific address, or indirectly by specifying a register
pointer. The contents of the register (or in some cases,
two registers) point to the desired memory location. In the
immediate mode, the data byte to be used is contained in
the instruction itself.
Each addressing mode has its own advantages and dis-
advantages with respect to flexibility, execution speed,
and program compactness. Not all modes are available
with all instructions. The Load (LD) instruction offers the
largest number of addressing modes.
The available addressing modes are:
•
Direct
•
Register B or X Indirect
•
Register B or X Indirect with Post-Incrementing/
Decrementing
•
Immediate
•
Immediate Short
•
Indirect from Program Memory
The addressing modes are described below. Each de-
scription includes an example of an assembly language
instruction using the described addressing mode.
Direct. The memory address is specified directly as a
byte in the instruction. In assembly language, the direct
address is written as a numerical value (or a label that has
been defined elsewhere in the program as a numerical
value).
Example: Load Accumulator Memory Direct
LD A,05
Reg/Data Contents Contents
Memory Before After
Accumulator XX Hex A6 Hex
Memory Location A6 Hex A6 Hex
0005 Hex
Register B or X Indirect. The memory address is specified
by the contents of the B Register or X register (pointer
register). In assembly language, the notation [B] or [X] speci-
fies which register serves as the pointer.
Example: Exchange Memory with Accumulator, B Indirect
X A,[B]
Reg/Data Contents Contents
Memory Before After
Accumulator 01 Hex 87 Hex
Memory Location 87 Hex 01 Hex
0005 Hex
B Pointer 05 Hex 05 Hex
Register B or X Indirect with Post-Incrementing/
Decrementing. The relevant memory address is specified
by the contents of the B Register or X register (pointer
register). The pointer register is automatically incremented
or decremented after execution, allowing easy manipulation
of memory blocks with software loops. In assembly lan-
guage, the notation [B+], [B−], [X+], or [X−] specifies which
register serves as the pointer, and whether the pointer is to
be incremented or decremented.
Example: Exchange Memory with Accumulator, B Indirect
with Post-Increment
X A,[B+]
Reg/Data Contents Contents
Memory Before After
Accumulator 03 Hex 62 Hex
Memory Location 62 Hex 03 Hex
0005 Hex
B Pointer 05 Hex 06 Hex
Intermediate. The data for the operation follows the instruc-
tion opcode in program memory. In assembly language, the
number sign character (
#
) indicates an immediate operand.
COP8SA Family
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