
ISCC
User Manual
UM011002-0808
44
•
Set FM mode WR14.
•
Set FM mode WR10.
3.7 CRYSTAL OSCILLATORS
For a given channel, if bit D7 of WR11 is set to 1, the crystal oscillator is enabled and a
high-gain amplifier is connected between the /RTxC pin and the /SYNC pin. While the
crystal oscillator is enabled, anything that has selected /RTxC as its clock source will auto-
matically be connected to the output of the crystal oscillator. This also makes the /S
YNC
pin unavailable for other use.
In synchronous modes, no sync pulse is output, and the External Sync mode cannot be
selected. In asynchronous modes, the st
ate of the Sync/Hunt bit in RR0 is no longer con-
trolled by the /SYNC pin. Instead, the Sync/Hunt bit is forced to “0.” The crystal oscillator
requires some finite time to stabilize and must be allowed to stabilize before it is used as a
clock source. The External C
rystal used should operate in parallel resonance.
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