Smart phone has bells, whistles

While most of us have some idea of what a "smart phone" is, the term remains ambiguous. I define a smart phone as one that offers Internet access through some means like Wi-Fi or cellular, has a relatively large color display and provides, among other things, video and still imaging.

By that definition, Sprint's PPC-6700 is definitely a smart phone. In addition to those features listed, it's built with a QWERTY keyboard and offers Bluetooth connectivity. A little sleuthing revealed that this handset was actually designed by HTC, an original design manufacturer located in Taiwan.

It's built around an Intel Xscale microprocessor (PXA270) and a Qualcomm cellular chip set (MSM6500). The total system measures 4.25 x 2.3 x 1 inch and weighs 6.1 ounces. Most of the handset's logic functions are handled by a 128-macrocell XC2C128 Xilinx CoolRunner-II complex programmable-logic device (CPLD) in a chip-scale package.

One of the latest features in this CPLD is on-the-fly reconfiguration, something Xilinx refers to as OTF. That means it's possible to deliver a new program into its flash memory while the part is operating. At some point, you throw the switch between the old pattern and new. Though this feature can be used while the handsets are out in the field, it gets an extensive workout while the system is being developed.

"To implement OTF in the field, because it's a radio, you can send the information through the radio, and the baseband captures the new image while it's operating," said Jesse Jenkins of Xilinx's CPLD product group. "A copy of that image is stored in the local RAM and then at some point you throw the switch, because the baseband can access the JTAG pins and drive the new pattern into the part. The part is not actually operating from the flash, but rather from a shadow RAM. So you can blast the new pattern into the flash."

HTC also uses a data gate in the CPLD. It lets HTC select any set of input pins that can be gated (blocked) in the future. For example, designers want to save power by shutting down sections of unneeded circuitry. To facilitate this, Xilinx lets system designers look at the input pins and pick the ones to shut down. By creating logic inside the CPLD, at a predetermined time or event, those pins can be selected and a gating signal driven to them so they can't switch until a release signal is sent out.

The CPLD can also, for security purposes, identify an event and basically shut out all the inputs. That means nothing would be running inside the device and no events could be created that would unblock the inputs. The only way to unblock them would be to power-cycle the part.

The less-glamorous functions the CPLD performs are for general-purpose I/O expansion. The Xscale processor used here comes ready to accept a set of standards, such as USB On-the-Go, IrDA, Bluetooth, I²C, SMBus and SPI.

Interfacing to all these standards can be difficult, since they require lots of pins. Or, if an interface comes around that wasn't available before, some extra pins may be needed. That's where CoolRunner-II comes in. To implement these new or additional I/Os, designers will often connect CoolRunner-II to an I²C interface and configure the CPLD's I/O pins like a shift register.

HTC designers could have implemented the CPLD as a keyboard scanner. At the time of the design, Xilinx was working on this feature, but on a much smaller scale. Because the PPC-6700 has a full keyboard, HTC went for a more traditional scanner.

While CoolRunner-II's basic architecture has not changed since the PPC-6700 was designed, some variations, like 32- and 64-macrocell parts, have been released. More I/O banks have been added as well.