Zilog Z16C35 - Manual (Page 50)

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 /SYNC
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 state 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 Crystal used should operate in parallel resonance.
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