FROM EDN EUROPE: HC08 microcontrollers go low power

Users of 8-bit microcontrollers now have a new option. Motorola's HCS08 family targets applications that need high performance (in the 8-bit space) but low power. Motorola claims that the new microcontrollers offer a unique combination of low-power, low-voltage operation; performance; and on-chip-debugging features (Picture). Running from supplies as low as 1.8V, the microcontroller has numerous low-power modes, down to a power-down state in which it uses only 20 nA from 2V; you can schedule wakeups with an internal timer (no crystal or external timing elements) that uses 700 nA at 2V. The internal clock source is accurate to better than 2% over temperature and voltage specifications. For many applications, this accuracy is good enough to preclude the need for a crystal or ceramic resonator. In operation, you can halt the processor in a variety of modes, trading off power demand for the possible need to reinitialise when operation resumes. The chips control active power by controlling the clocking of the processor core to as much as 20 MHz, depending on computation load. They also control edge speeds to minimise EMI. Motorola's Web site provides a spreadsheet calculator to estimate battery life given the duty cycle and the time it spends in different power states.

The core is HC08-code-compatible running at 20 MHz (2.1V) or 8 MHz (1.8V) maximum; Motorola claims the core is more code-efficient than its predecessor by 10 to 15% with single-byte multiply and divide. Motorola says the on-chip-debugging facilities are new for this level of device. All you need is a host PC, your target system, and a serial-connection BDM (background-debug-mode) pod. You get nonintrusive debugging with trace and single-stepping, full real-time emulation of all core functions, and the ability to manipulate register entries and memory locations on the fly. You can also access the on-chip debugging in a more limited way through one of the processor's serial ports. A free software package assists with code generation to configure the on-chip peripherals. The minimum investment to get to know the HCS08 is $49, which gets you a basic evaluation board, a serial cable, and a dedicated version of the CodeWarrior development suite. An investment of $199 gets you a BDM programmer/debugger module with a USB connection.

The first variants of the family will offer 1 to 4 kbytes of RAM space and 16 to 60 kbytes of onboard flash memory. The flash programs at 2.1V and reads at 1.8V; the device generates the voltages on-chip. Multiple variants will be in place by the end of 2003, and devices will cost $3.85 to $5.25 (10,000).

Motorola, www.motorola.com/mcu.