Dallas, Tex. Texas Instruments Inc.'s PCI Express (PCIe) x1 physical layer (PHY) chip has hit the market in volume, providing a low-cost PCI Express endpoint device for a wide variety of sectors such as data acquisition, industrial, networking, communication, medical, imaging, consumer and video.
The XIO1100 PCIe x1 PHY is designed to interface with low-cost FPGAs, including Xilinx's Spartan 3 and Altera's Cyclone II devices. The XIO1100 is compliant with the PCIe base specification revision 1.1 and PHY interface for the PCI Express (PIPE) 1.0. PIPE defines the standard interface between PCIe MAC and physical coding sublayer. For more on the specification revision, click here: www.pcisig.com/specifications/pciexpress/base
and on PIPE go to www.pciexpressdevnet.org/index.asp
The XIO1100 supports source synchronous clocking on both the Tx and Rx paths, which eases board layout constraints. It also supports DDR clocking, enabling customers to choose low-cost FPGAs that don't run faster than 125-MHz, according to Jawaid Ahmad, strategic product marketing manager for TI's digital interface business unit.
"Our interface has some differentiating features in it from the standard PIPE interface. We support source synchronous clocking, which means you have a separate clock for the receive and transmit parallel link between the FPGA MAC and PHY," Ahmad said. "You don't have to match all of the lengths of your signal to one clock lineyou can break it out into twothe receive bus and the transmit bus."
In addition to helping with board layout, source synchronous clock also helps when debugging the final design, he added.
The XIO1100 also supports both 8- and 16-bit parallel interfaces based on the PIPE architecture. When a design moves from 16- to 8-bits, the clock frequency has to be doubled. But since the XIO1100 offers DDR clocking, the frequency can be kept steady at 125-MHz. With 250-MHz-based FPGAs designs, an extra clock buffer is required. With TI's chip, designers don't have to worry about an extra clock buffer.
"The fact is there are FPGAs out there that if you want to have to run at 250-MHz, you can choose a low-cost FPGA. In a low-cost FPGA, you run it at 125-MHz and at 16-bit. And that option is available with our physical layer device," he said.
When the XIO1100 began to sample last year, TI said the XIO1100 would be available in production volumes in the first quarter of this year. When TI got to the first revision silicon, it found a bug that it decided to fix rather than issue errata. It fixed the bug in Revision 1.1 and took the device to PCI-SIG for compliance testing, which it since passed, Ahmad explained.
The XIO1100 is designed with two kinds of PCIe reference clocking modes, including a 100-MHz differential clock required by the standard PCIe specification, as well as a 125-MHz single-ended clock that is optional but has some benefits.
"For example, if you don't want to run reference clock directly from your south bridge, you could have a local reference clock in this case and we had to fix that in our revision silicon. So the single ended reference clocking was a bug that we had and we fixed it," he said.
It also supports enhanced low-power states by turning off clock in L1. It offers an access speed of 2.5-Gbits/s and a digital 8-bit I/F. TI's XIO1100 PCIe x1 PHY is also equipped with an adaptive equalizer to correct for signal degradation.
"When you're talking about 2.5-Gbits/s signaling rate for PCIe, you're talking very high-speed. You have to be careful in terms of your loss and jitter management on your board design," he said.
There are other x1 PHY devices that hit the market before TI's XIO1100. While Philips' PXI011A offers synchronous clocking, it doesn't support 16-bit, 125-MHz-based designs, only 8-bit and 250-MHz, he said.
Genesis Logic's GL9711 is PCIe-compliant, but only to the 1.0a specification. TI's XIO1100 is compliant to the 1.1 spec, which has tighter jitter requirements. Also, Genesis' device is housed in a 15-mm X 15-mm sized package compared with the 100-pin, 12-mm X 12-mm MicroStar BGA of the XIO1100.
In quantities of 1,000, the XIO1100 is priced at $7 each.
For more information on the XIO1100, please see www.ti.com/sc06138
Texas Instruments Inc., 1-972-644-5580, www.ti.com