SBAS495D June 2010 – August 2021 PCM9211
PRODUCTION DATA
The AUTO source selector is an automatic system that selects the DIR or ADC output based on specific DIR conditions set by Register 26h. The AUTO source selector is integrated in both the Main Port and the AUX output separately.
The typical behavior for the AUTO source selector is shown in Figure 7-20. This example is the default register setting for Register 26h. In this case, only Register 26h/AUNLOCK is selected.
When the DIR is unlocked, the ADC output is automatically routed to the Main Output Port.
Polarity of the CLKST signal is configured by Register 22h/CLKSTP. The default is active low, which means that clock source either changes from DIR to ADC, or from ADC to DIR.
If the DIR is locked, then the DIR output is routed to the Main Output Port automatically after tCLKST1. During that period, the output port is muted. tCLKST1 can be configured using Register 23h/ERRWT[1:0]. tCLKST2 is 50 ms, providing that an XTI clock of 24.576 MHz is applied.
If the DIR loses its lock a subsequent time, the ADC output is routed to the Main Output Port automatically after tXTIWT. Once again, the output port is muted during this time. tXTIWT can be configured using Register 23h/XTIWT[1:0].
The auto source selector can be triggered by the following changes in the DIR (Register 26h is used to select which variable to use as the trigger):
Figure 7-21 shows the Clock Tree Diagram for the AUTO source selector.