ATAR092_14 Datasheet, PDF (16/107 Pages) ATMEL Corporation – Bi-phase-, Manchester- and Pulse-width Modulator and Demodulator

4.5.2
Oscillator Circuits and External Clock Input Stage
The ATAR092/ATAR892 series consists of four different internal oscillators: two RC-oscillators,
one 4-MHz crystal oscillator, one 32-kHz crystal oscillator and one external clock input stage.
4.5.2.1
RC-oscillator 1 Fully Integrated
For timing insensitive applications, it is possible to use the fully integrated RC oscillator 1. It
operates without any external components and saves additional costs. The RC-oscillator 1 cen-
ter frequency tolerance is better than ±50% over the full temperature and voltage range. The
basic center frequency of the RC-oscillator 1 is f_O ≈ 3.8 MHz. The RC oscillator 1 is selected by
default after power-on reset.
Figure 4-13. RC-oscillator 1
RC-oscillator 1
RcOut1
Stop
Control
RcOut1
Osc-Stop
4.5.2.2
External Input Clock
The OSC1 or OSC2 (mask option) can be driven by an external clock source provided it meets
the specified duty cycle, rise and fall times and input levels. Additionally the external clock stage
contains a supervisory circuit for the input clock. The supervisor function is controlled via the
OS1, OS0-bit in the SC-register and the CCS-bit in the CM-register. If the external input clock is
missing for more than 1 ms and CCS = 0 is set in the CM-register, the supervisory circuit gener-
ates a hardware reset.
Figure 4-14. External Input Clock
Ext.
Clock
or
Ext.
Clock
OSC1
OSC2
Ext. Input Clock
ExIn
ExOut
Stop
Clock Monitor
RcOut1
Osc-Stop
CCS
Reset
Table 4-5.
OS1
1
1
x
Supervisor Function Control Bits
OS0
1
1
0
CCS
0
1
x
16 ATAR092/ATAR892
Supervisor Reset Output (Res)
Enable
Disable
Disable
4535E–4BMCU–05/07