Motorola uses expertise to develop 8bit MCUs to boost
Colin Holland takes a look at the first six members of Motorola'sNitron family of lower cost 8-bit microcontrollers that looks to widen the company's penetration outside automotive applications.
Motorola's Nitron series of six small-profile, 68HC08-based Flash 8-bit MCUs are available in 8- and 16-lead packaging and priced to extend the company's market reach in to lower cost applications.
Targeted at consumer electronics, industrial and automotive systems, the company's advances in manufacturing technology and high production volumes will provide the devices down to $0.70US with planned future derivatives under $0.50. This pricing level will allow the MCUs to compete against others with on-chip one-time programmable (OTP) memory, and in some cases, read only memory (ROM).
Also aimed at cutting costs, Motorola is making available free development tools - valued at more than $2,000 - for the Nitron Flash MCUs.
The Nitron (68HC908QT and 68HC908QY) family includes six devices. As well as the 68HC08 central processing unit (CPU), they include in-application and in-circuit re-programmable Flash memory (1.5K to 4K bytes), and a number of on-chip peripherals.
These include a two channel 16-bit timer system with selectable capture, compare and pulse width modulation (PWM), system protection such as selectable trip point low voltage inhibit (LVI) and auto-wakeup from STOP COP (Computer Operating Properly). A four channel 8-bit analog to digital converter (ADC) is included on the QT2/QT4/QY2/QY4 versions.
Nitron microcontroller family device schematic
In-application and in-circuit re-programmable, programming times are as fast as 32µs/byte. Block protection and security features will help customers guard intellectual property contained in software code. They allow embedded system designers to program late in the manufacturing cycle, make upgrades remotely in the field, and to quickly respond to the changing needs of their customers and the market with more flexibility than one-time programmable and ROM-based MCUs.
Available packages include 8-lead PDIP, 8-lead SOIC, 16-lead PDIP, 16-lead SOIC, and 16-lead TSSOP. The 16-pin TSSOP package offers 14 I/O pins in less PC board area than the 8-pin packages. Parts in 8-pin packages offer a 6-pin I/O port where each pin can be configured for use with on-chip peripheral systems, system functions, or general purpose I/O. The 16-pin packages offer a second 8-bit general purpose I/O port.
Oscillator options include an internal trimmed oscillator that needs no external connections or components, an R-C option that uses one external connection and an external resistor to set the frequency, a standard external crystal option which uses two external pins, or an external oscillator option which uses one pin to connect an external clock source. The internal oscillator reduces system cost and reduces board space while eliminating the EMI that is generated from external clocks.
On-chip peripheral functions include a full-featured 2-channel 16-bit timer system and a 6-pin keyboard interrupt system.
Application programs can use some pages of FLASH memory as EEPROM while using the rest for program memory. System integration functions are also fully supported by the on-chip power-on reset (POR), COP watchdog, and low-voltage-inhibit (LVI) circuitry.
Based on the 68HC08 architecture, an extension of the 68HC05 architecture that has existed for more than 20 years, the Nitron products feature a CPU that allows efficient, compact modular coding in assembly or C language.
The efficient instruction set includes multiply and divide while 16 flexible addressing modes include stack relative with 16bit stack pointer.
The 4 channel, 8-bit ADC provides conversion in 17µs and eases interfacing to analog inputs such as sensors.
There are up to 13 bi-directional I/Os and one input. These high current I/Os allow direct drive of LED and other circuits, eliminating external drivers and cutting system cost. The keyboard scan with programmable pull-ups removes the need for external glue logic when interfacing to simple keypads.
The low-voltage inhibit with selectable trip points improves the reliability by resetting the MCU when voltage drops below the trip point.
The Timer Interface Module on the 908QT microcontrollers is common to all of the HC08 Family. It has the capability to perform multiple channels of input capture, output compare or pulse width modulated (PWM) output, with a resolution down to 125ns.
This is a powerful feature rarely found on a microcontroller of this size, and can be used to provide much faster and more accurate timing functions than can be achieved using software routines, as well as greatly simplifying development.
The 908QY devices provide a similar set of features, but in a variety of 16-pin packages. A tiny 16-pin TSSOP package allows up to 14 pins to be used as inputs or outputs, while occupying a space less than 35mm2.
Development support is taken from the larger M68HC08 devices and includes a monitor ROM and an on-chip breakpoint module. The monitor ROM supports traditional MON08 monitor mode and includes utility routines for programming and erasing the on-chip FLASH memory.
Monitor mode was developed as a feature of the M68HC08 MCU architecture to provide basic in-circuit debugging, as well as programming of nonvolatile memories.
Monitor mode is not a substitute for full chip emulation, but it allows a low-cost connection to a host computer, which sends commands serially to the MCU. These commands perform read and write operations on the MCU's registers and memory. The system developer does not have to be concerned about the monitor commands since these are embedded in the programming/debugging tools.
However, there are some practical limitations that must be considered when designing a system that will be programmed or debugged in-circuit using monitor mode.
Monitor mode uses a single I/O pin to communicate with a host PC. This pin is controlled by the monitor mode firmware in the MCU. The pin is switched between input and output as it emulates the serial protocol to the PC. This limitation only applies during monitor mode. As soon as the chip is released from monitor mode, the pin reverts to its I/O function.
Monitor mode must have a clock frequency that will allow the MCU to match the serial baud rate of the PC. In most cases the debug connector can provide a clock signal that can overdrive the crystal on the target board.
The Metrowerks CodeWarrior Development Studio Special Edition for the 68HC908QT/QY family is available at no charge to registered users of Motorola's web site and contains tools from several vendors.
It includes an optimized 68HC908QT/QY Family C compiler, assembler, debugger, simulator, flash programmer, and an auto-code generator for on-chip peripherals.
A special-edition evaluation board that features a battery powered 68HC908QT4 device, LEDs, potentiometer, push button, access to all I/O for user-provided interfacing, a software demo and application code.
The board includes an 8-pin plastic DIP device that is pre-programmed with a monitor access program and a small demonstration program. The monitor access program allows the board to be interfaced to a host personal computer (PC) for debug and FLASH programming operations.
The small demonstration program shows how to use the timer, A to D, and keyboard interrupt functions of the microcontroller.
A voltage regulator is included to provide 5V to the MCU from a 9V transistor battery. An RS232 level shifter and a DB9 connector are included to interface the evaluation board to the serial port of a PC. A single MCU pin is used to communicate with the host PC at a standard 9600 baud rate. A potentiometer is connected to an A to D pin, a pushbutton switch is connected to a keyboard interrupt pin, and an LED is connected to a general purpose output pin so a small application program can demonstrate these on-chip systems.
A CD is provided which includes complete documentation, application notes, and development software. A complete CodeWarrior development environment is included along with FLASH programming tools, an M68HC08 assembler, and a C compiler (memory size limited to 4Kbytes which is the size of the FLASH memory in the Nitron series parts.
Third-party programmers such as the Cyclone stand-alone programmer from P&E Microcomputer Systems can measure the on-chip oscillator frequency in the application system and program a trim adjustment factor into the FLASH memory. Depending on the oscillator option used, these MCUs can operate at up to 32MHz.
Motorola also offers 68HC08 Web-based training as part of a range of services that are designed to make it easy for customers to design-in and use the microcontrollers.
Market provides opportunities for 8-bit MCUs with Flash memory
According to specialist market researchers, SEMICO, Motorola was the top seller of 8bit MCUs in 2001 with 24% of the total world market. In 2002 sales of 8-bit MCUs are expected to grow 4.4% with another jump of 12.2% in 2003, partly achieved by taking market share form the 4-bit MCU sector.
SEMICO believes that the 8bit devices need to address a broad market requirement with a large number of peripheral configurations for specific market needs. While automotive and consumer applications drive the market there is an increasing use of 8-bit devices in IC cards.
At present around 30% of 8bit MCUs have Flash memory, up from just over 20% in 2000, and expected to rise to over 40% by 2005. At present 8-bit MCUs provide 43% of the revenue and 60% of the units of the total microcontroller market.
At present nearly two thirds of Motorola's products are used in the automotive sector but there is a drive to expand the use in standard applications faster to provide equality.
To gain market share, Motorola expects to displace existing suppliers and capture segment growth to dominate the 8bit market in proliferating low cost applications.
Motorola has shipped more than 5 billion 8bit MCUs since 1993 and also has several families of 16-bit and 32-bit devices. By 2010 the company expects the average person to interact with over 350 microcontrollers daily.
Published in Embedded Systems (Europe) November 2002
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