DM-COP8/20D National Semiconductor, DM-COP8/20D Datasheet - Page 31

• Manufacturer Part Number: DM-COP8/20D
• Description: CABLE FOR DEBUG MODULE 20-DIP
• Manufacturer: National Semiconductor

Specifications of DM-COP8/20D

• Accessory Type: 20-DIP Target Cable
• For Use With/related Products: MetaLink Debug Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *DM-COP8/20D

Each microcontroller has a set of instructions. The user can organize particular
instructions in a logical order to create a program. The microcontroller follows this
program to perform a given task. The contents of a microcontroller instruction set vary
with various microcontrollers.
Opcodes
Mnemonics
Categories of Instructions
Opcode fields/Multiple Byte Opcodes‘
An opcode field is a group of bits within an opcode used to represent one specific part of
an instruction. Typically the bits in an opcode are broken into groups or fields. Most
instructions usually consist of at least two fields: opcode field and address field.
Addressing Modes
Implied
Immediate
1. Arithmetic/logic/shift (ADD/AND/RRC)
2. Transfer of control (JP, JMP)
3. Memory reference (LD)
4. Bit manipulation (SBIT)
5. Stack control (PUSH)
6. Conditional/Test (IFEQ)
Numeric codes in the instructions that represent the actual operation to
be performed by the CPU are called operation codes (or opcodes for
short). An opcode is actually a group of bits which tell the microcontrol-
ler to perform a particular operation (a code word for a given operation).
For example; 64 might mean clear the accumulator.
Names assigned to particular operations are called mnemonics. Each
mnemonic is associated with a particular opcode. A user may specify a
mnemonic such as ADD rather than the opcode 84. The mnemonic is lat-
er translated into opcodes which the microcontroller can decode. Using
mnemonics makes writing code easier. For example, the mnemonics LD,
ADD, JP, CLRA represent the operation load, add, jump, and clear accu-
mulator, respectively.
Data to be used as an operand is specified directly
The location/value of the operand(s) is specified
implicitly in the definition of the instruction.
Example: CLR A, SC
in the instruction.
Example: LD A, #023 or AND A, #0FF
MICROCONTROLLER BASICS
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