SBAS495D June 2010 – August 2021 PCM9211
PRODUCTION DATA
An external clock source (CMOS or crystal/resonator) is known as the XTI source. The XTI source can be either a CMOS logic source, or a crystal resonator (internal circuitry in the PCM9211 can start the crystal resonating). Whichever clock source is used, it must be 24.576 MHz.
The PCM9211 uses the XTI source as a reference clock in order to calculate the sampling frequency of the incoming S/PDIF stream. It is also used as the clock source in XTI clock source mode.
When using a resonator as an XTI source, the following points should be considered:
When using an external oscillation circuit with a CMOS output, the following points should be considered:
Figure 7-11 shows the connections for the XTI and XTO pins for both a resonator connection and an external clock input connection.
In XTI mode, the output clocks (SCKO, BCKO, and LRCKO) are generated from the XTI source clock.
Register 24h/OSCAUTO controls whether or not the internal oscillator functions while it is not required. When using the DIR as a clock source, the XTI source is not required; thus, the internal oscillator can be switched off. There is a constraint, however, that when the DIR wide mode is being set (for example, in 192-kHz support), the XTI is always used. The sampling frequency calculator also requires the XTI source.
XMCKO (the XTI clock buffered output) provides a buffered (and divided) XTI clock that can be output to MPIO_A. Register 24h/XMCKEN controls whether the XMCKO should be muted or not, and Register 24h/XMCKDIV controls the division factor.