COP8SA-DM National Semiconductor, COP8SA-DM Datasheet - Page 21

• 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
DESCRIPTION OF MICROCONTROLLER BUILDING BLOCKS
1.7.1
Program Memory
Program memory contains the microcontroller program.
There are several types of program memory—ROM, OTP/EPROM, EEPROM.
Control
Logic Unit
IR
Program
Memory
Stack
PC
Internal Data Bus
Figure 1-3 Program Memory Section
Structure
The number of bits per address location and number of memory locations varies from one
microcontroller type or family to another (8/2/14/16 -bit by 0.5k, 1k, 2k, 4k, etc.).
Program Counter (PC)
The program counter is used by the CPU to address program memory locations that
contain the program instructions. Every time an opcode (binary representation of an
instruction) is fetched (read) from memory, the program counter in incremented
(advanced by one) so that it points to the next byte following the opcode (assuming 8-bit
memory organization, an assumption used throughout the rest of this document. Some
program instructions require more than one byte. In that case, the program counter
supplies the address, the second byte is fetched from memory, and the program counter
is incremented. Each time the CPU performs a fetch operation, the program counter is
incremented; thus, the program counter always points to the next byte in the program.
Therefore, after all bytes required for one complete instruction have been read, the
program counter points to the beginning of the next instruction to be executed. The
program counter size is base on the size of the program memory.
MICROCONTROLLER BASICS
1-9