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Asterisk sirrix PCM Connector Description
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All Sirrix.PCI cards are equipped with a PCM bus. The PCM bus allows to use hardware switching functionality across cards installed in the same system. This functionality is available even between cards of different type, like PCI4S0 and PCI2E1. The PCM bus also allows to use the resources of all cards (e. g. hardware echo cancellation or bus mastering) for all connections made by Sirrix.PCI cards in the system.
As the PCM bus is a fundamental function of the Sirrix.PCI cards, the PCM bus must always be properly set up.
If only one Sirrix.PCI card is installed in the system, no further action is required.
If more than one Sirrix.PCI card is installed in the system, the PCM connector located on each card shall be used to interconnect all installed Sirrix.PCI cards. The following diagram depicts the pin-out of the PCM connectors on Sirrix.PCI4S0 and Sirrix.PCI2E1 cards.
IMPORTANT: All Sirrix.PCI4S0 installed in a system in combination with Sirrix.PCI2E1 card shall have a firmware version >= 060904. The firmware version number is displayed in syslog when loading the "sirrix_pfic" kernel module and can also be displayed by using the Asterisk CLI command "srx show system".
| PCM_D15 | GND |
| PCM_D14 | GND |
| PCM_D13 | GND |
| PCM_D12 | GND |
| PCM_D11 | GND |
1 | PCM_D0 | GND | | PCM_D0 | GND |
| PCM_D1 | GND | | PCM_D1 | GND |
| PCM_D2 | GND | | PCM_D2 | GND |
| PCM_D3 | GND | | PCM_D3 | GND |
| PCM_C1536 | GND | | PCM_C1536 | GND |
| PCM_C8 | GND | | PCM_C8 | GND |
1 | PCM_nFSC | GND | | PCM_nFSC | GND |
| PCM_BCL | GND | | PCM_BCL | GND |
1 | PCM_D4 | GND | | PCM_D4 | GND |
| PCM_D5 | GND | | PCM_D5 | GND |
| PCM_D6 | GND | | PCM_D6 | GND |
| PCM_D7 | GND | | PCM_D7 | GND |
| n/c | GND | | PCM_D8 | GND |
| n/c | GND | | PCM_D9 | GND |
Installing PCM bus
For setting up the PCM bus in multi-card systems, you need to connect a 1:1 ribbon cable between all boards boards in order to keep clocks synchronized. Connect the cable to the header labeled "Sirrix.PCM-Interface". You have to take care that the plugs are connected all in the same direction (check pin 1, usually the colored wire) and with the same alignment, effectively connecting pin 1 to pin 1, pin 2 to pin 2 and so on. You can use any ribbon cable with enough pins, e.g. a straight IDE cable not having crossings. Do not use 80-wire IDE cables, these WILL NOT work.
Note for systems with multiple PCI4S0 cards:Unfortunately, convenient connectors are not available, so you need to use "larger" ones with more pins. But as long as the unused pins are the same on all cards, you are fine.
If you place the cards side-by-side (top view, PCI connectors bottom, brackets left, PCM-Interface header right), you should connect a cable from left to right without twisting it. If it looks the same on all cards you are right.
Do not use cables that are too long or cables with too many open connectors, otherwise you might get reflections on the cable and the system will not work. We already tested 10 cards with a cable of about 100 cm in length.
Note for systems with both PCI4S0 and PCI2E1 cards:If cards of different type (PCI4S0 _and_ PCI2E1) are installed in the system, please attach the cable to the PCI4S0 cards with "open" pins as depicted above: The pins PCM_D15 through PCM_D10 would be simply left "open" on the PCI4S0 cards whilst connected as usual on the PCI2E1 cards.
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