To have the IMSCSA generate SREF-8K, add the macro SCSA_SREF_MASTER to the mode argument for the scsa_mode function. For example:

    scsa_mode (scsa, SCSA_MASTER | SCSA_SREF_MASTER);
    scsa_mode (scsa, SCSA_SLAVE | SCSA_SREF_MASTER);

To have the IMSCSA synchronize to the SREF-8K signal from the backplane, add the macro SCSA_SREF_SLAVE to the mode argument for the scsa_mode function. This is only valid of the primary mode is SCSA_MASTER. For example:

    scsa_mode (scsa, SCSA_MASTER | SCSA_SREF_SLAVE);

In order to use this mode, the IMSCSA module must be revision 4 number stored in the module's EEROM. Revision 4 IMSCSA modules have a 14.087178 MHz crystal installed with a small capacitor across the crystal's leads to tune it to within 32 parts-per-million accuracy. Revision 3 IMSCSA modules have the crystal installed but must be upgraded with the additional tuning capacitor or a more accurate crystal.

The TDM subsystem should be configured to derive its clock from the IMSCSA module using the pci_tdm_timing function. For example:

    int scsaclk = 8;     /* 8.192 MHz SCSA and TDM clock */
    int tdmframe = 128;  /* 128 TDM slots per TDM frame */
    PCI_MOD *scsa;
    PCI_TDM *tdm;

    scsa = pciopen ("pci0b");
    tdm  = pci_tdmopen ("pci0");
    scsa_init (scsa, scsaclk);
    scsa_mode (scsa, SCSA_MASTER | SCSA_SREF_SLAVE);
    pci_tdm_timing (tdm, TDM_MODCLK(1), scsaclk, 8, -tdmframe, 16);