San Mateo, Calif. Useful architectures achieve a kind of immortality in the microcomputer world. The situation is not unlike that of the New Englander who claimed to be using the very ax his forebears brought over on the boat from England. "It's had three new heads and seven new handles since then, but . . ."
Microcontroller units also tend to be upgraded a block at a time as user needs change, until they would be unrecognizable to their original designers. But they remain familiar indeed to their devoted programmers.
The Z8 MCU of Zilog Inc. (San Jose, Calif.) is a case in point. Originally a contemporary of the Intel 8051 and Motorola 6805, the Z8 has survived and even thrived in its own ecological niches, primarily in very low-cost, consumer-related control applications, such as TV sets.
But survival has meant evolution. Recently, Zilog upgraded the execution unit of the Z8 to achieve 20 MHz three times the rate of the original Z8. The company has also moved to flash program memory. And, last week, Zilog revealed yet another set of upgrades to what is now called the Z8 Encore! family, related primarily to power management and I/O flexibility.
The Z8 Encore! offers up to 64 kbytes of flash, up to 4 kbytes of internal SRAM, on-chip DMA, 10-bit A/D capability, SPI, I2C and UART ports, IrDA-complaint codecs, and the usual counter/timers.
The enhancements add several features. The first is voltage brown-out circuitry that can be selectively shut down with the chip in "stop" mode, thereby conserving power. Also, the on-chip clock oscillator has been made more flexible; it now accepts external RC networks or ceramic resonators.
In the I/O department, the number of channels on the 10-bit A/D converter has been increased to 12, and the I/O pads have been rendered tolerant of 5-volt levels.
The devices are available in sample quantities. Prices vary by configuration. A device with 64 kbytes of flash in a 44-pin LQFP is priced at $5.06 each in thousands.