C511_1 Datasheet, PDF (17/128 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Fundamental Structure
2.1 CPU
The SAB-C511/513 microcontrollers are efficient both as a controller and as an arithmetic
processor. It have extensive facilities for binary and BCD arithmetic and excels in its bit-handling
capabilities. Efficient use of program memory results from an instruction set consisting of 44% one-
byte, 41% two-byte, and 15% three-byte instructions. With an 8 MHz clock, 58% of the instructions
are executed in 1.5 µs.
The CPU (Central Processing Unit) of the SAB-C511/513 consists of the instruction decoder, the
arithmetic section and the program control section. Each program instruction is decoded by the
instruction decoder. This unit generates the internal signals controlling the functions of the individual
units within the CPU. They have an effect on the source and destination of data transfers, and
control the ALU processing.
The arithmetic section of the processor performs extensive data manipulation and is comprised of
the arithmetic/logic unit (ALU), an A register, B register and PSW register.
The ALU accepts 8-bit data words from one or two sources and generates an 8-bit result under the
control of the instruction decoder. The ALU performs the arithmetic operations add, substract,
multiply, divide, increment, decrement, BDC-decimal-add-adjust and compare, and the logic
operations AND, OR, Exclusive OR, complement and rotate (right, left or swap nibble (left four)).
Also included is a Boolean processor performing the bit operations as set, clear, completement,
jump-if-not-set, jump-if-set-and-clear and move to/from carry. Between any addressable bit (or its
complement) and the carry flag, it can perform the bit operations of logical AND or logical OR with
the result returned to the carry flag.
The program control section controls the sequence in which the instructions stored in program
memory are executed. The 16-bit program counter (PC) holds the address of the next instruction to
be executed. The conditional branch logic enables internal and external events to the processor to
cause a change in the program execution sequence.
Accumulator
ACC is the symbol for the accumulator register. The mnemonics for accumulator-specific
instructions, however, refer to the accumulator simply as A.
Program Status Word
The Program Status Word (PSW) contains several status bits that reflect the current state of the
CPU.
Semiconductor Group
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