Test Connections

Geotest's new GX3700 and GX3700e Flex DIOs expand its product line of user programmable, Altera-based FPGA modules. Both products use the Altera Stratix III FPGA, which can support SerDes data rates to 1.25GHz/sec and I/O data rates to 700MHz. Additionally, both cards include 256K x 32 of SSRAM as well as integrated DMA capability. By offering the same high performance FGPA architecture in either PXI or PXI Express formats, customers with an installed base of PXI chassis are not required to update their existing systems and chassis to take advantage of the higher performance FPGA available with the GX3700e.

Both cards offer identical capabilities and include the following key features:

On-board 80 MHz oscillator for use as an FPGA timing reference
Access to the 10 MHz PXI clock and the 100 MHz PXIe clock (GX3700e only)
Access to all PXI trigger and local bus signals
16 MB of on-board flash memory

For applications that require high data throughput, the GX3700e offers the ability to stream data to and from the host controller via the PXI express' X4 interface at rates in excess of 800MB/s. The GX3700e can also be used for peer to peer data transfer applications when combined with a compatible PXI multi-computing controller which resides in a PXI Express peripheral slot – providing a high performance data acquisition, generation and analysis subsystem.  

Both the PXI and PXI express cards utilize a high performance base board/expansion board architecture, which allows users to develop their own custom circuitry within the compact, single-slot, 3U form factor without relying upon bulky, external interface boards. The expansion board interfaces to the base board via a high performance connector interface, allowing users to take advantage of the Stratix III's high data rates. Both the GX3700 and GX3700e are supplied with a generic expansion board which provides the user with access to the FPGA's I/O via (4) 68 pin SCSI 3 interfaces located at the front panel of the card. Access via the front panel to these signals includes:

160 I/O signals, with direction programmable on a per channel basis.
Up to 64 of the I/O signals can be configured for differential operation.
(4)  I/O can be configured a 4 singled ended clocks or 2 differential clock inputs.

As noted above, customers can create their own custom circuitry or PXI / PXIe instrument by designing a custom expansion board for their specific application. And since the GX3700's expansion board and associated front panel connections are part of the expansion board's design (see Figure 1), users have the freedom to choose multi-pin or coaxial connections, depending on the application. In addition, various IP (intellectual property) design cores are available both from Altera and third parties, offering designers an easy way to create a wide range of digital and mixed signal interfaces.

Figure 1 – GX3700e with Expansion Baord

Some examples of custom applications that employ a custom expansion board include:

Multi-channel D to A and A to D source / measure instrumentation
USB and Ethernet channel support using the Stratix III's built-in SerDes capabilities
High speed serial data stream generation and analysis including bit error rate test
Custom digital bus emulation
Serial bus emulation : including I2C, SPI, & CAN
Video generation

Users can design the FPGA by using Altera's free Quartus II Web Edition tool set or for more complex designs; they can use Altera's Quartus II subscription edition software. Once the FPGA design is compiled, the configuration file can be loaded into the FPGA via the PXI bus interface or via an on-board 16MB EEPROM – providing users with an easy way to incrementally design / test / modify their FPGA code. Geotest offers a full set of software tools, including an interactive UI, for the GX3700 and GX3700e to facilitate the loading of the compiled design. Predefined registers are used as well to provide interactive control to the user FPGA — simplifying overall development and deployment of the design and eliminating the need for the user to incorporate the PCI bus interface as part of his or her overall FPGA design. The GX3700 and GX3700e combine the flexibility and performance associated with FPGA based designs with the standardization and open architecture of the PXI platform.

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Geotest-Marvin Test Systems, Inc.
1770 Kettering
Irvine, CA 92614

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