Electronic Design

Low-Power PC-On-A-Chip Uses A Failsafe Startup

Consuming just half a watt at 133 MHz, the MachZ PC-on-a-chip from ZF Linux incorporates all major PC-compatible peripheral controllers, SDRAM support, and a PCI and ISA bus. Its ZF Failsafe boot ROM and ZF-Logic both support multiple jumper-selectable startup procedures. The MachZ can even start without SDRAM installed by using the processor's 8-kbyte cache memory.

The MachZ is ideal for embedded applications that are being developed or downsized from a PC platform. Its ability to run operating systems like Linux provides access to readily available and well-tested network protocol stacks and other software resources.

The ZF Failsafe boot ROM incorporates fixed- and flash-memory support. The fixed portion initially configures the MachZ peripheral controllers and the ZF-Logic. The flash element includes dual watchdog timers. One timer is available to the flash-memory boot program, while the fixed failsafe boot program uses the other timer to detect a flash-memory boot failure. When failures occur, the fixed portion determines what to do by using the ZF-Logic. This includes downloading a new program into flash memory if necessary.

The MachZ uses Z-Tag to download a new program into flash memory. Z-Tag operates through a number of MachZ peripheral interfaces, with a top transfer rate of 2.5 Mbits/s. This is fast enough for production-line programming. Multiple source options enable programming over a network via a modem or from a CD-ROM.

Failsafe operation is only part of the MachZ's appeal. Its collection of PC-compatible peripheral controllers is another. For instance, the EIDE and floppy-disk controllers can be used to boot from disk drives. The other peripherals look like the usual ATX motherboard complement, including a parallel port, dual serial ports, dual USB ports, an IrDA port, and PS/2 keyboard and mouse ports. The DMA and IRQ support also is PC-compatible. The I2C bus support and eight GPIO lines are useful, but they're not part of the normal PC-compatible complement.

The SDRAM interface operates as a 16- or 32-bit bus supporting up to 256 Mbytes of memory. With the PCI bus, designers can use the latest peripherals. The ISA bus provides a simpler interface that's often more suitable for embedded applications.

The Cyrix 486 processor core required some customization to work with the north and south bridge architecture, which is normally used with the newer Pentium processors. Given the appropriate peripherals, the Cyrix core will handle all PC-compatible operating systems, from Linux to Windows.

The MachZ has the usual power-management features, including wakeup on USB, keyboard, or mouse activity. The device also can check the eight general-purpose IOs. However, it doesn't include graphics and PCMCIA support. By using external graphics support, it enjoys a wider choice of interfaces. The EIDE interface supports Compact Flash, providing an alternative to PCMCIA.

Additionally, this integrated development system includes Red Hat Linux 6.2, plus LynuxWorks BlueCat Linux development tools or Wind River's VxWorks. It comes with Phoenix Technologies' PhoenixBIOS as well.

The MachZ is made on a 0.24-µm process. Packaged in a 35- by 35-mm, 388-pin BGA, it costs $60 in small quantities. The price falls to the mid-$30 range in large quantities.

ZF Linux Devices Inc., 1052 Elwell Ct., Palo Alto, CA 94303; (800) 683-5943; fax (690) 965-4050; www.zflinux.com.

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