COP8SA-DM National Semiconductor, COP8SA-DM Datasheet - Page 24

• Manufacturer Part Number: COP8SA-DM
• Description: MODULE DEBUGGING FOR COP8SA
• Manufacturer: National Semiconductor

Specifications of COP8SA-DM

• Module/board Type: Debugger Module
• For Use With/related Products: Cop 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *COP8SA-DM

1.7.3
The key function of a CPU is to perform instruction fetch/decode/execute.
Arithmetic Logic Unit (ALU)
The arithmetic logic unit is a binary adder. It performs all the arithmetic and logic
functions in the microcontroller. The destination for all such operations is the
Accumulator (A). The two inputs to an operation are the accumulator and either an
immediate data as specified by an instruction or, more commonly, the contents of data
memory locations. The one-bit carry register (C register) sometimes is a third input to
the ALU.
Status/Control Registers
The status and control registers are special-purpose registers used to store the state of
the microcontroller. The control bits are manipulated by the user program to place the
microcontroller and its peripherals in particular states. The status bits are read by the
application program to inform microcontroller/user of the current state. Examples
include:
1-12
Fetch
Decode
Execute
MICROCONTROLLER BASICS
1. A carry bit, which indicates whether the last operation performed by the ALU
2. Interrupt enable bit, which tells the microcontroller whether an interrupt is
3. Interrupt pending bit, which tells the program whether a particular interrupt
Microcontroller CPU
Stack Pointer
POP instructions.
generated a carry.
enabled.
occurred.
The program counter (PC) addresses a location in program memory con-
taining an instruction. This instruction is latched into a special instruc-
tion register (IR). The PC is incremented to point to the next available
instruction.
The instruction in the IR is decoded. The bits of the instruction relate to
specific actions. Each bit or group of bits is used to determine the appro-
priate control signals to activate in order to cause the execution of the
instruction.
The control signals go out to all parts of the microcontroller, causing the
desired action to take place.
Return Address High
Return Address Low
Before
Empty
Stack
Stack Pointer
Empty
Empty
Empty
Stack
After