COP8AME9_14 Datasheet, PDF (84/102 Pages) Texas Instruments – COP8AME9 8-Bit CMOS Flash Microcontroller with 8k Memory, Dual Op Amps, Virtual EEPROM, Temperature Sensor, 10-Bit A/D and Brownout Reset

COP8AME9, COP8ANE9
SNOS930F – MARCH 2001 – REVISED MARCH 2013
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ADDRESSING MODES
The instruction set offers a variety of methods for specifying memory addresses. Each method is called an
addressing mode. These modes are classified into two categories: operand addressing modes and transfer-of-
control addressing modes. Operand addressing modes are the various methods of specifying an address for
accessing (reading or writing) data. Transfer-of-control addressing modes are used in conjunction with jump
instructions to control the execution sequence of the software program.
Operand Addressing Modes
The operand of an instruction specifies what memory location is to be affected by that instruction. Several
different 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 disadvantages 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 description 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
Memory
Accumulator
Memory Location
0005 Hex
Contents
Before
XX Hex
A6 Hex
Contents
After
A6 Hex
A6 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] specifies which register serves as the pointer.
Example: Exchange Memory with Accumulator, B Indirect
X A,[B]
Reg/Data
Memory
Accumulator
Memory Location
0005 Hex
B Pointer
Contents
Before
01 Hex
87 Hex
05 Hex
Contents
After
87 Hex
01 Hex
05 Hex
84
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