High-speed low-latency serial bus?

Might be worth looking at MOST. Fibre-optic, pretty high-speed, and 25mbit.

pete

If its point-to point (no possibility of collision), Ethernet will give you full duplex, electrical isolation and determinism - plus low cost.

Latency is more complicated as this depends on where the data needs to go, host CPU/OS interrupt issues etc etc

Peter Wallace

These unique requirements appear to call for a proprietary protocol (including isolation solution based on the parts that are readily available for high speed transitions) based on a serial link connection (clock, data, and framing signal) found in processors with built-in serial-to-DMA integrated peripherals.

Is your remote device able to provide the clock for the serial transmission and 20 KHz sampling? Is this a multi-drop configutation, in which case you would require timing information broadcast by the master station?

If you are interested, I can provide the details based on the Motorola MPC8xx communications capabilities.

Alternatively, or as a special-case, the Ethernet solution using the

Regards,

- Thierry Moreau

CONNOTECH Experts-conseils inc.

Tel.: (514)385-5691 Fax: (514)385-5900

e-mail: snipped-for-privacy@connotech.com

snipped-for-privacy@connotech.com (Thierry Moreau) wrote in news: snipped-for-privacy@posting.google.com:

Yep. I'm looking at Analog Devices' SPORT in TDM mode at 30 Mbps for a few nodes, but will need something else for more.

Multi-drop, single-master, all nodes in one room. I'm trying to build a multi-input multi-output system where several output nodes depend on several input nodes and system state, with a high update rate. The environment might be electrically hostile. (Stupid customers, bad building wiring, electrostatic issues, etc.)

Thanks, I've got an 8xx manual around here somewhere. I'm hoping to find something less tied to a specific CPU but that's not imperative.

Are you suggesting gigabit Ethernet, wired point-to-point to eliminate non- determinism? That might work.

If you have only a single master, you do not have to worry about determinism in an Ethernet network. With about 50 bytes minimum frame size (5 us @100 Mbit/s) you should be able to transfer about 200 000 frames/s or 10 frames at 20 kHz.

If that is not enough, an you have a large number of nodes, look at systems similar to Interbus-S and EtherCAT, in which data can be collected from a large number of nodes into a single message frame.

Paul

How much bandwidth do you need per node? How much latency is too long?

Do you require a bus or star cabling configuration? What's the rate and size of each data block? Polled or asynchronous?

How much jitter can you tolerate?

Ethernet is a decent fit for a lot of your requirements, and it works in fairly hostile environments over good distances. Media converters are readily available / cheap for fiber use in high EMI environments.

Ethernet switches are the cure to a lot of Ethernet's negatives - they let you run in full-duplex mode to eliminate contention. If a single

There are a couple 100Mbps chipsets with ISA bus; most are PCI, and you'll probably find that all Gig-E are PCI.

Richard wrote in news: snipped-for-privacy@azglobal.com:

All excellent questions. I'll take those back to my team and try to establish more precisely what we need.

It does look attractive as a dedicated private bus.