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10.2.8.4.6 Clock Failure Detection
10.2.8.4.6.1
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).
SPRUGX9 – 15 April 2011
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Preliminary
© 2011, Texas Instruments Incorporated
Multichannel Audio Serial Port (McASP)
Architecture
1053
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