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what a daisy chain is?

Hi everyone, It seems a simple question.But I still have something i cannot completly understand.

A daisy chain is often used a mulidrop topology, which need an end-termination. And, source-termination doesnot work properly in daisy chain,because the device in the middle of the chain would get a plateau. So, in a design , i should figure out minimul distance between, say two receivers. in other words, beyond what distance between two receivers , source-termination should not be used, and this topology can be named a daisy chain?

---- ------ ------- Driver---------revceiver_1-----------------------receiver_2

---- ------- -------- |-------------distance---------|

thank you all!

Reply to
jasonleehan
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It's a repeater, so up to the point at which the signal level falls below a specific point.

In digital it would be called bit-error-rate.

Reply to
Spurious Response

The problem lies in how source termination works. By setting the source (termination) resistor equal to the impedance of the line, it causes a wave to be launched on to the line that is at 50% amplitude. When the signal hits the (single) receiver which is approximately an open circuit the amplitude doubles, hence appearing as normal at the receiver end. The signal than travels back (reflected - again at 50% amplitude) towards the source where it is squelched by the termination resistor.

The receiver sees the full amplitude because of the interference caused by the original signal and its reflection. Any devices in the middle of the chain would see a 50% waveform, twice.

The purpose in load end termination in the daisy chain is to allow all devices in the chain to see the full amplitude signal - once and to prevent reflections on the line which will interfere with transmission.

Reply to
Noway2

There are two kinds of daisy-chain: one (like SCSI or thinwire 10base2 Ethernet) supports multiple attachment to a backbone, which is terminated at each of two ends. The other is based on repeaters (Firewire uses these) so all links are terminated at each end, but repeaters make another port available to continue the chain.

This isn't clear to me. In the case of SCSI, there was a 'stub' allowed of four inches, so a very short (4 inch) bus could operate with only one terminator. In the case of 10base2 Ethernet, that WASN'T allowed, because the terminators determined some signal levels that had to be predictable in order to detect collisions.

In neither case is 'source termination' a recognizable feature; all the devices on the chain can be sources, and it's the CHAIN that has terminations.

Reply to
whit3rd

That's not a daisy chain - that's a multi-drop. A daisy chain looks like this: -------- --------------------- ------------- Driver_0-------revceiver_1--Driver_1-------receiver_2--etc. -------- --------------------- ------------- where each item has an input and output, and the connection goes from one's output to the other's input, and so on.

As far as multi-drop, you have to look at driver capacity and timing and stuff like that.

Hope This Helps! Rich

Reply to
Rich Grise

Gods, what a blazing idiot / asshole. Did you read far enough down the hit list to find wikipedia? It was above this NG wasn't it? Wasn't it informative enough?

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 JosephKK
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Reply to
joseph2k

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