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PMC module churns through high-res realtime data conversion

Posted: 15 Aug 2005 ?? ?Print Version ?Bookmark and Share

Keywords:pmc module? pci mezzanine connector module? sheldon instruments? si-c6713dsp-pmc? texas instruments?

Can crank through 1,800MFLOPS of DSP number crunchingThese new PMC (PCI mezzanine connector) modules from Sheldon Instruments' are screamers. In fact, one of Sheldon's SI-C6713DSP-PMCs can crank through 1,800MFLOPS (peak) of DSP number crunching without breaking a sweat. While much of that performance accrues to the Texas instruments tms320c6713 chip, a lot of the board's strength also rests with the architecture.

The hardware interface between the host PCI bus and the DSP is implemented with PLX Technology's PCI9056's chip. It's a 32-bit 66MHz PCI bus mastering I/O accelerator. The board uses this device to implement control logic that arbitrates the appropriate timing between the DSP's EMIF (external memory interface) bus, boot SRAM/flash, and the PCI9056's local bus.

Hardware and software handshaking
A combination of hardware and software handshaking takes place to support many data transfer schemes, where the host side can be selected to operate in one mode and the DSP in another. From the host PCI side, the SI-C6713DSP-PMC module provides three modes. It supports a target/slave mode, a PCI-initiated bus mastered transfer mode with the PCI9056 acting as the bus master, and a bus mastering mode with the DSP acting as the PCI bus master.

From the DSP side, there are also three modes. These include a standard programmed I/O mode, an asynchronous DMA (direct memory access) mode, and a synchronous DMA mode.

Host target/slave mode accesses are performed when the DSP is either disabled or enabled. While the DSP is disabled, the host uses the target/slave mode to load an initialization COFF (common object file format) file to the card's boot memory, as well as to access expansion daughter modules. After DSP activation, any combination of data transfer modes can be used on either side. PCI bus mastering is the most efficient, with minimal host intervention.

Not mentioned in Sheldon Instruments' press release are the various memory configurations you can get from any of the six flavors of this product. They're configured with conventional 144-pin SO-DIMM (small outline dual in-line memory module) sockets, and these accommodate 3.3V non-buffered PC133 SDRAM.

Note that these SO-DIMMs are identical to those used in many laptops. Significantly, all six of the SI-C6xDSP-PMCs support half of the capacity on 64MB, 128MB, 256MB and 512MB sizes. You can socket only as much memory as your application really needs, saving money in the process.

Another way to cost-effectively use a SI-C6xDSP-PMC is to let it play with various I/O modules. The board's expansion connectors support roll-your-own I/O, as well as off-the-shelf pre-configured multi-function I/O modules from Sheldon. The company has a number of daughter cards supporting multi-channel analog and digital I/O, and data conversion. Add-ons let you configure four to 64 channels of 16-bit A/D conversion or D/A conversion.

Sheldon's 16-bit resolution successive approximation SI-MOD68xx A/D family, for example, can plug right in.

Cards in this family feature differential or single-ended analog inputs, with groupings of channels using its own MUX and PGA (programmable gain amplifier). Each input can be individually programmed for differential or single-ended operation, not limiting you to an all-or-nothing configuration. Sampling rates can range from DC to as high as 250kHz, with an aggregate to 1MHz.

The SI-MOD68xx cards also confer up to sixteen 16-bit analog outputs, with update rates to 180kHz. These bipolar outputs deliver as much as 10V, and the circuitry includes a three-pole smoothing filter. Sample clocking is internal or external, using either a divide-by-N counter or a DDS (direct digital synthesizer) option. Clocking can also be set up to sync multiple cards.

Support and adjuncts
As the company's press statement notes, the PMC comes with development tools, both from Sheldon Instruments and from Texas Instruments. The former's QuVIEW and QuBASE tools are realtime DSP-resident libraries. QuVIEW is a realtime accelerator for National Instruments LabVIEW, and QuBASE a realtime accelerator for VisualBASIC. QuBASE runs under Windows 98, Windows 2000, and Windows XP. QuVIEW also runs under Linux.

If you use the SI-C6713DSP-PMC module as a DSP eval board, Sheldon Instruments includes free sample DSP and Windows/Linux device driver source code. This code works in TI's development environment.

Sheldon's SI-Filter-8 accessory is a PCI bus card with eight channels of excitation, amplification, and anti-alias filtering. It can condition both single-ended and differential input signals. It comes with application software and drivers for Windows and Linux.

Finally, Sheldon offers a number of terminal strip accessories, cables, and even a PC104/Plus-to-PCI adapter card that works in desktop systems. The card permits the insertion of a PC104/Plus card into a system configured with conventional PCI slots.

- Alex Mendelsohn

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