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Dieter Spaar spaar at mirider.augusta.deHello Andreas, On Fri, 17 Apr 2009 12:45:50 +0200, "Andreas.Eversberg" <Andreas.Eversberg at versatel.de> wrote: > if you need clock signals, you can use the C4IO clock line of the ISDN > cards. they clock 4096khz. you can use them to transfer clock from one > card to another or to mesure the clock. the E1 card has this clock on > one pin of the PCM connector. (see data sheet) the C4IO is also > available on the HFC-PCI single port card. with an oscilloscope you can > compare. > > in order to retieve the clock from E1 interface in NT-mode, you need to: > > modprobe hfcmulti port=0x200 debug=0x40000 > > watch the dmesg about init process of controller. this will override the > default behavior: provide clock to the NT interface. > > i would suggest to use a resistor of 1K to protect the e1 card. the > signal must not look good, we just need the shift of both signals. Thanks for this tip. I already though about the E1 clock, but its below the 10 MHz limit of the HP8922. I think I have to build a simple frequency counter (I don't have one) and use the reference clock of the HP8922. BTW, there is also a GSM frame pulse available at one of the connectors (one of the J01 pins, I have to look it up). OK, maybe a simple frequency counter is a good reason to finally do something usefull with my FPGA boards ;-) Best regards, Dieter -- Dieter Spaar, Germany spaar at mirider.augusta.de