RE: Why do ISO-11898-2 and ARINC 825 never mention split termination?
"John Dammeyer" <[email protected]>
| Newsgroups | gmane.comp.hardware.bus.can |
|---|---|
| Message-ID | <[email protected]> |
Hi Dave, Long time… Nice document. Very comprehensive. But misses the point about bit rate and bus length. I'd like to see a reference for lines 10..15 other than just ethereal app notes etc. The data sheet 120 node maximum drive for the 82C250 for example is from the parallel combination of the 120 devices worst case input impedance in parallel with two 120 ohm resistors. There is nothing scientific about reducing the number of nodes based on cable length or stub length. Inductance and capacitance play a much larger role and to get that as low as possible usually means buying specialty cable which is thick, not very flexible and expensive. The problem I have with those magic rules is they then tend to get quoted without reference by someone else. Then their document is quoted by someone else and pretty soon we have a general rule that everyone quotes without any underlying basis. Then we see emails with people arguing that the maximum number of nodes on a bus is limited to 48 with no direct connection to your document; which has no reference either. Still other than that a good source for a lot of information. Best Regards John Dammeyer From: [email protected] [mailto:[email protected]] On Behalf Of David Harris Sent: December-07-14 10:29 AM To: [email protected] Subject: Fwd: [CANLIST] Why do ISO-11898-2 and ARINC 825 never mention split termination? Our document for the physical layer of OpenLCB (model railroad bus) discusses this, and has some references: http://www.openlcb.org/trunk/specs/CanPhysicalTN.pdf David -- Archives and useful links: http://groups.yahoo.com/group/CANbus Subscribe and unsubscribe at www.vector.com/canlist/ Report any problems to <[email protected]>