Datasheet

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External Reference Resonator/Crystal Oscillator Clock Option
External
Clock Signal
(toggling 0-1.8 V)
OSCOUTOSCIN
Crystal
OSCOUTOSCIN
(a) (b)
C1
(A)
C2
(A)
TMS470R1B1M
16/32-Bit RISC Flash Microcontroller
SPNS109A – SEPTEMBER 2005 – REVISED AUGUST 2006
The oscillator is enabled by connecting the appropriate fundamental 4–10 MHz resonator/crystal and load
capacitors across the external OSCIN and OSCOUT pins as shown in Figure 6 a. The oscillator is a single-stage
inverter held in bias by an integrated bias resistor. This resistor is disabled during leakage test measurement
and HALT mode. TI strongly encourages each customer to submit samples of the device to the
resonator/crystal vendors for validation. The vendors are equipped to determine what load capacitors will
best tune their resonator/crystal to the microcontroller device for optimum start-up and operation over
temperature/voltage extremes.
An external oscillator source can be used by connecting a 1.8-V clock signal to the OSCIN pin and leaving the
OSCOUT pin unconnected (open) as shown in Figure 6 b.
A. The values of C1 and C2 should be provided by the resonator/crystal vendor.
Figure 6. Crystal/Clock Connection
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