Solving the 8-Bit to 32-Bit Transition Problem

Page Contents:

[ The Performance Path | At the Core | Compatible Peripherals, Packaging and Tools | FAQs ]

Transitioning from an 8-bit to a 32-bit MCU has historically been a design ordeal for users. Many factors contribute to establishing a continuum of processor capability, however, established expertise in both arenas is essential to understanding the users' needs in each area. This article will explain how recognizing the problem initially resulted in modifying the silicon hardware and software design philosophy and, ultimately, in defining 8-bit and 32-bit products with compatible packaging, peripherals and tools. The silicon design methodology will simplify performance upgrades in numerous end products.

The Performance Path
Microcontrollers address applications that range from very simple electromechanical replacements with solid state technology to extremely complex controls that require sophisticated 32-bit MCUs. Some companies offer products to solve either or both ends as well as applications in between, transitioning from an 8-bit to a 16-bit to a 32-bit MCU has never been easy. Today, as the low end 8-bit and mid-range 16-bit requirements for MCUs are expanding rapidly, the answer could be found in a number of low-cost 32-bit architectures. However, for users migrating up from 8 and 16-bit MCUs, the 32-bit architecture feels very different to them. Usually, new hardware tools are required and the migration is costly and time consuming.

From the extensive experience in both 8-bit and 32-bit MCUs, Freescale has defined an approach that simplifies the transition for customers and allows the reuse of software and tools. Mid-range performance MCUs, especially 16-bit processors, are frequently defined by price point, power consumption, set of peripherals, and/or performance level required for a specific application and not by bits. In most cases, customers only care about solving the system problem. By bridging this gap with an 8-bit to 32-bit continuum, customers can start with today's system requirements and plan for tomorrow's improvements without making significant changes and leverage prior tool and software investments.

 

At the Core
The ability to transition seamlessly between 8-bit and 32-bit cores starts at the 8-bit level. The well-established S08 core provides the foundation for 8-bit performance and an extensive peripheral library. The new RS08 core reduces the size of the S08 central processing unit (CPU) by 30% and provides an even greater range for the continuum. Targeting low-cost applications where electronic control replaces electromechanical devices, this smaller, more efficient core takes advantage of the peripherals developed for numerous HCS08 applications.

At the high end, a new 32-bit V1 ColdFire core provides the missing link in the transformation chain. The V1 platform includes the V1 core, local memories (Flash and the SRAM), a background debug module (BDM) and a bus bridge. The bus bridge provides the interconnection between the core's local high-speed bus and the slave peripheral modules. It is the bus interface that converts one protocol to the other.

 

 

The V1 platform portion will typically be running twice as fast as the peripheral modules. In addition to providing the functionality of the bus protocol conversation, the bus bridge module also serves as the clock domain boundary. Using well-established and easy-to-use 8-bit peripherals with a 16-bit internal architecture and a 32-bit core makes linking the 8-bit and 32-bit portfolios easier.

The choice to move from an 8-bit to a 16-bit MCU is based on a number of considerations. With today's processing technology, the 32-bit V1 core costs roughly the same price as a 16-bit core. However, the available performance is significantly higher. Even though the bits are not a continuum, the performance and pricing are.

 

Compatible Peripherals, Packaging and Tools
A number of factors contribute to a seamless transition from an 8-bit to a 32-bit architecture. The improvements start at the core and involve peripherals and packaging as well as development tools.

Since its initial implementation over a decade ago, the ColdFire instruction set architecture (ISA) has changed from an optimization philosophy for 32-bit operands with some support for 8-bit and 16-bit operands to one of expanded and improved support for handling 8-bit and 16-bit operands. For the V1 class of applications, this is particularly important for users migrating from 8-bit and 16-bit applications. At the processor core level, it is important for the implementation of the instruction set to directly address some of the issues that involve efficient handling of 8-bit and 16-bit operands.

The V1 core microarchitecture has a number of improvements relative to the V2 ColdFire that improve the performance of those instructions handling 8-bit and 16-bit operands. Not only does the V1 support those instruction types, their execution is optimized in the V1 pipeline. In applications with a significant amount of data referenced to 8-bit and 16-bit operands, both the instruction support and fast execution time for those instructions provides a considerable performance improvement.

The continuum takes advantage of existing peripheral IP. Peripheral blocks connect to a common bus structure so complete reuse of S08 IP is ensured. The investment that both Freescale and users have made in the 8-bit domain is preserved. While timing and other issues may need to be evaluated, this approach leverages existing driver software for peripherals.

 

 

 

One of the challenges to keeping the pin count the same was the background debug mode (BDM). The BDM in a traditional ColdFire was implemented on a three-pin serial interface (clock, data-in, data-out) and a fourth pin provided breakpoint capability. The BDM provides the ability to serially insert commands that read/write registers or read/write memory, run and stop the processor, and more. Because the S08s have restricted pin availability, the functionality in the classic ColdFire was remapped into a single pin interface for the V1 exactly like the S08. The second part of the debug story has to do with ColdFire support for realtime trace.

For the V1, the realtime trace operation had to be modified. The CPU outputs processor status information, addresses, and debug data, but instead of immediately outputting this information like the V2 and other ColdFire MCUs, the V1 incorporates a PST (processor status) and debug data trace buffer as part of the V1 core. With this approach, users program start and stop conditions for recording information that comes out of the trace port and the information gets collected, compressed, and loaded into the trace buffer. Then the trace buffer can be read out using the single pin BDM capabilities. This is a very powerful concept that preserves the realtime trace capabilities by capturing events spanning hundreds of machine cycles, but maps them into a technique that works with a single pin interface.

The biggest challenge to an 8-bit to 32-bit transition is the tools. The main development tool has to be interchangeable and provide 8-bit or 16-bit customers the same simple look and feel as they move up in complexity to 32-bit. With a new version of the CodeWarrior Development Studio, an 8-bit S08 can be removed and replaced with a 32-bit V1 ColdFire using exactly the same tool, same cable, and the same set of CodeWarrior tools. The user simply recompiles C-developed code.

 

What Users Will Do Differently
With the controller continuum, a customer who starts with an S08 microcontroller can transition easier than ever before to a 32-bit architecture. With the transition, users get the processing power of a 32-bit core that is significantly higher than that of an 8-bit S08 core. The 32-bit V1 provides an estimated performance improvement of 10X over the 8-bit S08 architecture running at the same speed (20MHz).

This amount of performance improvement opens up new application areas and can change the way a company plans their long-term product roadmap. Based on the ease of use of the 32-bit architecture, this is suited for 8 or 16-bit users seeking an easy entry to 32-bit performance.

The continuum approach also works for 32-bit users looking to reduce power consumption and cost in their application. Using a new low-voltage low power process, the V1 provides a very low power consumption 32-bit MCU for both standby and run current. The power density is also expected to be unique and create new applications.

Since the V1 ColdFire products have 10x the performance of S08 devices, it will be possible for products to increase performance within an application without increasing frequency which can be beneficial to applications sensitive to EMC such as appliances and washing machines.

These approaches have been discussed and validated with many customers. Once designers evaluate the potential for implementing this new methodology in their design process, they immediately envision new ways to address future designs.

 

Getting There from Here
The continuum builds on extensive 8-bit S08 as well as 32-bit ColdFire experience by taking action on the feedback from customers which has led to a number of improvements to the instruction set, hardware (including debug capabilities), and development tools that makes an upward transition simple.

In most embedded control designs, there rarely is one major factor that swings a design decision one way or the other. The decision typically depends on an accumulation of many minor details. By optimizing power, size and performance, peripheral usage and development tools, the 8-bit to 32-bit controller continuum delivers unique capabilities to system designers. With the ability to seamlessly transition upward, the continuum provides companies a long term planning capability that promises to change the product roadmaps in many industries.

 

 

Frequently Asked Questions

What's Coldfire?
In 1994, the innovative ColdFire Microprocessor Family was added to Freescale's Legacy 68K Family tree. This new variable-length RISC 68K Family architecture delivers the aggressive price/performance required by the cost-sensitive embedded market. In striving to meet the needs of the market with this innovative architecture, Freescale evaluated high-level source code from many 68K embedded systems customers. Based on the results of this study, a reduced instruction set and addressing modes were identified which created an efficient environment for processor operation. Like most RISC processors, the majority of ColdFire processor instructions execute in a single cycle.

The variable-length RISC ColdFire architecture gives customers greater flexibility to lower memory and system costs. Because instructions can be 16-, 32- or 48 bits long, code is packed tighter in memory resulting in better code density than traditional 32- and 64-bit RISC machines. More efficient use of on-chip memory reduces bus bandwidth and the external memory required, which results in lower system cost.

Small and inexpensive, the static ColdFire core also lowers system cost because it is completely synthesizable and easily integrated with memories, system modules, and peripherals. Because of its portable nature, the ColdFire core is easily targeted to different process technologies, making it attractive as a product for third-party licensing. Freescale is currently developing strategic alliances with other companies.

With its architectural relationship to the 68K Family, customers using 68K products should consider a standard ColdFire product as their next solution. Because the ColdFire processor instruction set is a subset of the 68K Family instruction set, existing 68K customers find that designing with ColdFire microprocessors is a smooth transition. Current 68K tool developers should also find that the newest member of the 68K family is easy to support. Moreover, the ColdFire architecture has a product performance roadmap that extends beyond the 68K Family to provide 400 MIPS in the year 2001. Thus, ColdFire processors provide a performance path for every member of the 68K Family.

The ColdFire product portfolio offers a wide mix of performance, price, integration and debugging capabilities for embedded designers looking to upgrade their systems. The ColdFire product development tools offers are unmatched. its integration possibilities are limited only by imagination, and its 20-year history of 68K legacy is something no other competitor can offer. With these features to work with, the ColdFire architecture is in a leadership position in the 32-bit embedded space. You are invited to become a part of its success.

For more information click HERE

 

Learn more about Coldfire Architecture
Implementation Methodology Designed for Reuse

• All cores are 100% fully synthesizable
• Parameterizable - all options exist within a single design description
• Configurable
• Generic local-memory controllers support a range of sizes
• Choose size using compiled memory arrays
• Hierarchical architecture
• Multiple buses provide layers of bandwidth + modularity
• Standard internal bus structure provides simple interface
• Design-for-Test
• Muxed D-FF rising-edge clocked design
• ATPG scan vectors for stuck-at, speed testing
• BIST test methodology for memories
• Deployment focused on soft macro RTL + support of hard macros

For more information click HERE

 

Learn About FSL's S08 8-Bit Devices

HCS08

High-performance and low power, the HCS08 does not sacrifice performance to provide low power 1.8V operation. HCS08 Features - Multiple power management modes, including a 20 nanoamp (nA) power-down mode.

• A zero-component auto-wakeup from "stop" to help reduce costs and reduce power to 0.7 microamp (µA) - Up to 40MHz CPU/20MHz bus at 2.1V and 16MHz CPU/8MHz bus at 1.8V
• A programmable internal clock generator with temperature and voltage compensation (typical drift < 2%) designed for reliable communications, fast start up and reduced system cost
• In-application reprogramming and data storage via third-generation 0.25µ flash technology
• High integration including four serial communication ports, up to 8 timer/PWMs, and an 8-channel 10-bit analog-to-digital converter specified down to 1.8V

For more information click HERE

 

What's Codewarrior?

1. Codewarrior for Coldfire

The ColdFire family of microprocessors benefits from extensive support by a world-class development tools suite through leading third-party tools developers. In addition, Freescale, Quadros Systems and Metrowerks have partnered to provide a comprehensive, networked, embedded control solution based on the ColdFire MCF528x Family, OpenTCP stack, RTXC™ Quadros operating system and CodeWarrior™ for ColdFire.

RTXC Quadros for the MCF528x Family includes a real-time operating system (RTOS) supporting both thread- and task-based kernels. It also includes extensive networking support—Ethernet driver; Internet protocols such as IP, UDP, TCP, ICMP, ARP and DHCP; and application-level protocols such as embedded Web server, Trivial FTP server for remote firmware download, SMTP to send e-mail alerts and SNTP to retrieve current-time information from a network NTP server. Three versions of the software are available at a range of prices and functionality.

The Special Edition is free and preloaded into the internal Flash with the purchase of the M5282EVB or available for download for registered users of the Freescale Web site. The CodeWarrior for ColdFire development tools suite from Metrowerks includes a compiler, assembler, debugger, project manager and build system. Trial versions of the tools are provided with the development kit.

For more information click HERE

 

2. Codewarrior for 8-Bit

Freescale's CodeWarrior™ Development Studio for HC(S)08/RS08 with its world-class integrated development environment (IDE) has been reengineered to enhance the user experience. The CodeWarrior tool suite includes built-in features and utilities that improve ease of use, speed and accessibility over previous versions of CodeWarrior software development tools. Using the CodeWarrior development tool, product developers can get better quality products to market faster and more economically.

A quick start guide eases installation and helps create a first example project, and more than 100 example projects are available to assist in your design efforts. The Project Wizard can be used to create a working project (Assembly or C) in as few as seven mouse clicks, and users can change target microcontrollers and the debug/Flash programming connection in an open project.

The award-winning CodeWarrior IDE goes well beyond basic code generation and debugging— expect it to help streamline application design from the moment you open the box. It features an intuitive, state-of-the-art project manager and build system; a highly optimized compiler; a graphical, source-level debugger; integrated profiling capabilities; a full chip simulator and more.

CodeWarrior Development Studio for HC(S)08/RS08 Microcontrollers v5.1 is available for download at www.freescale.com, and a useful updater utility enables Web access for updates and service packs.

For more information click HERE

 

What's BDM? Learn more about this FSL unique Background Debug Module that's embedded on the micro!

Freescale has defined a standard 6-pin connector that allows an interface pod to be connected to any target HCS08 or RS08 Family MCU. This connector definition is also used in the HC12 and HCS12 Family MCUs and was derived from the 10-pin interface found on Freescale's high performance 16-bit and 32-bit MCUs. The 6-pin interface has connections for the BKGD pin, RESET, VDD and ground (GND). The BKGD pin does not require an external pullup resistor since it has an on-chip pullup. The connector includes an optional reset signal so that a development system can remotely force a target system reset. A VDD connection is optional and allows the BDM interface pod to get power from or to the target system.

For more information click HERE

 

Coldfire V1 – Making 32-Bit as Easy as 8-Bit

Coldfire V1 Roadmap

 

Related Articles on the 8- to 32-Bit Seamless Migration Story

Control the Continuum

Freescale Brings 32-Bit Performance to the 8-Bit Market
Freescale has launched the ColdFire V1 core, which it claims blends 32-bit performance with the ease of use of an 8-bit microcontroller. The move is a response to increasing performance and memory requirements in such applications as medical, industrial and motor control.

Core charts 8/32-Bit MCU Migration Path
Freescale Semiconductor Inc. has developed a 68K/ColdFire microcontroller core that for the first time will enable OEMs to easily upgrade from 8- to 32-bit capability with the same on-chip peripheral functions and tool sets.

 

Learn More

ColdFire Overview Brochure

ColdFire V1 Fact Sheet

ColdFire V1 White Paper