Freescale: 8-Bit Microcontroller Family

Overview

HCS08

High-performance and low power, the HCS08 provides low power 1.8 V operation whilst maintaining a very respectable performance. The HCS08 family features multiple power management modes, including a 20 uA power-down mode.

Internally, the S08 instruction set is upward compatible with the 6805, with the addition of stack indexed addressing modes. (Instructions using the SP register have opcodes prefixed with the byte 0x9E). It has a single eight-bit accumulator, A, one eight-bit index register, X, or one sixteen-bit index registers, HX (formed from the combination of H and X registers), a condition code register, a 16-bit stack pointer, and a program counter. For compatibility with the 6805 which does not have an H register, the most significant byte of the HX register, H, is cleared during reset, and H is the only register not stacked automatically when entering any ISR (Interrupt Service Routine).

Some instructions treat the H and X registers as a combined 16-bit HX register. Unlike the 6805, the stack can be placed anywhere in memory using appropriate instructions. The standard method of programming or debugging the S08 family is via a standard 6-pin BDM interface. A wide variety of peripherals is available for different members and/or packages. SCI, SPI, 10-bit or 12-bit A/D, (C)PWM, Input Captures are common with most members, but no external bus is available.

RS08

The RS08 core is a reduced version of the S08 central processing unit (CPU) that has been specifically designed for small pin-count devices with under 16KB memory. Thirty percent smaller than the S08 CPU, it is more efficient and cost-effective for simple electro-mechanical devices that are migrating to fully solid-state electronic operation or portable devices that have evolved into smaller or even disposable versions.

Ideal for emerging applications like simple electro-mechanical devices that are migrating to fully solid-state operation, portable devices that have evolved into smaller or even disposable versions. Functions that are not required for such applications have been stripped from the S08 core and remaining operations have been enhanced to improve the efficiency of extremely small controllers.

Thirty percent smaller than the S08 core (can be shaken through a pepper shaker), the RS08 core has been streamlined by limiting the counter and address bus to 14 bits, replacing vectored interrupt capability with a global interrupt flag register and by removing: Stack point and H:X register along with the associated instructions and addressing modes, Multiply, Divide and binary-coded decimal instructions, Arithmetic logic shift operations (logical shifts and rotates have been retained), Bits in condition code register and associated conditional branching instructions.

The RS08 core deepens the Freescale 8-bit portfolio, and offers pin-for-pin compatible 8-bit and 32-bit devices that share peripherals and a common set of development tools. It also allows mechanical and electronic product developers to come up with the totallyunexpected—creating advanced, cost-effective electronic applications that have no precedent and disposable products with surprisingly sophisticated functionality.