ST7FLCD1 datasheet(15/95 Pages) STMICROELECTRONICS

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ST7FLCD1

Central Processing Unit (CPU)

This CPU has a full 8-bit architecture and contains six internal registers allowing efficient 8-bit data

manipulation.

2.1

Main Features

● Enable executing 63 basic instructions

● Fast 8-bit by 8-bit multiply

● 17 main addressing modes (with indirect addressing mode)

● Two 8-bit index registers

● 16-bit stack pointer

● 8 MHz CPU internal frequency (9 MHz maximum)

● Wait and Halt Low Power modes

● Maskable hardware interrupts

● Non-maskable software interrupt

2.1.1

CPU Registers

The 6 CPU registers shown in Figure 5 are not present in the memory mapping and are accessed

by specific instructions.

Accumulator (A)

The Accumulator is an 8-bit general purpose register that holds operands and results of arithmetic

and logic calculations. It also manipulates data.

Index Registers (X and Y)

In indexed addressing modes, these 8-bit registers are used to create either effective addresses or

temporary storage areas for data manipulation. (The Cross-Assembler generates a previous

instruction (PRE) to indicate that next instruction refers to the Y register.)

The Y register is not affected by interrupt automatic procedures (not pushed to and popped from the

stack).

Program Counter (PC)

The program counter is a 16-bit register containing the address of next instruction the CPU

executes. The program counter consists of two 8-bit registers:

PCL (Program Counter Low which is the LSB)

PCH (Program Counter High which is the MSB).

ST7FLCD1 Datenblatt(PDF) 15 Page - STMicroelectronics