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Functional Description
22.3.10.4.6 Clock Failure Detection
22.3.10.4.6.1 Clock-Failure Check Startup
It is expected, initially, that the clock-failure circuits will generate an error until at least one measurement
has been taken. Therefore, the clock failure interrupts, clock switch, and mute functions should not
immediately be enabled, but be enabled only after a specific startup procedure. The startup procedure is:
1. For the transmit clock failure check:
(a) Configure transmit clock failure detect logic (XMIN, XMAX, XPS) in the transmit clock check control
register (XCLKCHK).
(b) Clear transmit clock failure flag (XCKFAIL) in the transmit status register (XSTAT).
(c) Wait until first measurement is taken (> 32 AHCLKX clock periods).
(d) Verify no clock failure is detected.
(e) Repeat steps b–d until clock is running and is no longer issuing clock failure errors.
(f) After the transmit clock is measured and falls within the acceptable range, the following may be
enabled:
(i) transmit clock failure interrupt enable bit (XCKFAIL) in the transmitter interrupt control register
(XINTCTL).
(ii) transmit clock failure detect autoswitch enable bit (XCKFAILSW) in the transmit clock check
control register (XCLKCHK).
(iii) mute option (XCKFAIL) in the mute control register (AMUTE).
2. For the receive clock failure check:
(a) Configure receive clock failure detect logic (RMIN, RMAX, RPS) in the receive clock check control
register (RCLKCHK).
(b) Clear receive clock failure flag (RCKFAIL) in the receive status register (RSTAT).
(c) Wait until first measurement is taken (> 32 AHCLKR clock periods).
(d) Verify no clock failure is detected.
(e) Repeat steps b–d until clock is running and is no longer issuing clock failure errors.
(f) After the receive clock is measured and falls within the acceptable range, the following may be
enabled:
(i) receive clock failure interrupt enable bit (RCKFAIL) in the receiver interrupt control register
(RINTCTL).
(ii) mute option (RCKFAIL) in the mute control register (AMUTE).
3811
SPRUH73H–October 2011–Revised April 2013 Multichannel Audio Serial Port (McASP)
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