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      • 10 bit long sync word - configuration and over air bit pattern

        baadamff | 01/26/2015 | 05:29 AM

        Question

        How to configure 10 bit long sync word?

        Which bits sent exactly?

        Answer

        For example :
        Set SYNC_BITS.BITS[31:24] property (0x1101) to 0xB2
        and SYNC_BITS.BITS[23:16] property (0x1102) to 0xD5.

        Set SYNC_CONFIG2.LENGTH_SUB property (0x1105) to 0x03, it means the Sync word is 6 bits less.

         

        In this case the radio sends the following over air pattern:

        01001101 10

         

        First the radio sends the 0xB2 in least significant bit order:

        bit 24, bit 25, bit 26, .. ,bit 30, bit 31

        01001101

         

        Then the 0xD5 in least significant bit order, but without last the 6 bits:

        bit 16, bit 17.

        10

         

        So the not sent bit are: bit 18, bit 19, .. , bit 22, bit 23.

         

        These are marked with red below:

         

        Sync_registerview.png

         

        The over air pattern can be reviewed also in WDS

         

          WDS_sync.png

         

         

      • EZRadioPRO and shared nIRQ interrupt pins

        erunruh | 01/22/2015 | 01:39 PM

        Question

        Can the nIRQ interrupt output pin on an EZRadioPRO device be shared with other devices?

        Answer

        Or to ask the question another way, is the nIRQ output pin on EZRadio/EZRadioPRO (Si4455 and Si446x devices) an open-drain pin that may be direct-tied in parallel with nIRQ pin(s) of other chips or devices?

         

        No.  The nIRQ output pin on Si4455 and Si446x chips is a driven pin (i.e., a push-pull output architecture) whenever the chip is in an active state.  The only state in which the nIRQ pin is not driven to a logic level is when the chip is in SHUTDOWN mode (SDN pin = HIGH).  In this state, the nIRQ output pin is not directly driven to a logic level, but is internally pulled HIGH by a weak pull-up resistor.  Thus if the system application is designed such that the nIRQ pins of multiple devices are directly tied together in parallel, the system must ensure that the EZRadioPRO chip is in SDN mode when the other device(s) are functional, and vice versa.