Continuing on from my barrage of questions yesterday... The netjet BRI card appears to contain the Tiget320 PCI interface controller, which is in turn connected to a Siemens ISAC-S chip, which does the frame encoding and decoding.
My understanding of ISDN is that data is transmitted in frames of 16 data bits (B1) + 16 data bits (B2) + 4 data bits (D) + some synchronisation. 4000 of these frames are received per second, which gives us the 16 * 4000 = 64kbps rate for the B channels and 4 * 4000 = 16kbps rate for the D channel. To get the zaptel timing of 1000 interrupts/second, the card needs to be able to generate an interrupt off (at least) every 4th frame. If the best it could do was to generate an interrupt per frame, how much would that kill the system in interrupt servicing? Looking at the way some of the zaptel drivers work, this timer interrupt is the only interrupt that is cared about, and the card is polled per interrupt rather than being truly interrupt driven. Or maybe I just haven't looked at enough drivers... Can anyone tell me what sort of pre-processing needs to be done to the raw data from a [BP]RI card into the zaptel driver? I assume that the D channel needs to be decoded from the raw bits on the line (or does it...?), but does the zaptel logic need anything more than raw bits from the B channels? I'm not really familiar with PRI cards, but in the BRI space there are 'passive' cards, 'semi-active' card, and 'active' cards... can zaptel cope with different levels of processing being done on the card, or does it like to do it all itself? Or none of it itself? I've had a look around for this sort of documentation, and it doesn't appear to exist except in the code, which is fine, it will just take me a bit longer :) Thanks James _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- Asterisk-Dev mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
