From: [email protected] (Lars Poulsen) Subject: Timing in ISDN-CPE with multiple BRI ports
Greetings to fellow TREG'ers ... In the design of a CPE with multiple BRI ports (for the purposes of this discussion, think of it as a small PBX with a handful of BRI ports to the central office), we became aware of a peculiarity in the Motorola MC145574 device: When we select TE slave mode timing, it becomes unable to do D channel contention. In our device, we have a handful of BRI ports connected to the system's TDM highway; we elect one to be the timing master, and tell the rest to take timing off the shared bus. This appears to be okay with Motorola's corresponding U-interface part, or with Siemens' part. The lack of D-channel contention is not functionally crippling, it just limits the device to point-to-point operation per ETS 300125 Annex A. I am, however concerned that approval of equipment with such a restriction may require a waiver that may not be portable across the EU. Has anyone else encountered this problem ? Would you be willing to discuss how you solved it ? (The obvious workaround would be to put a FIFO between the MC145574 and the TDM bus, and tell the 145574 he's master; but that seems like a potentially large kludge.) / Lars Poulsen [email protected] +1-805-562-3158 OSICOM Technologies (Internet Business Unit) (formerly RNS) 7402 Hollister Avenue Manager of Remote Access Engineering Goleta, CA 93117 Internets designed while you wait
