ATA6020N ATMEL Corporation, ATA6020N Datasheet - Page 16

• Manufacturer Part Number: ATA6020N
• Description: Low-current Microcontroller For Watchdog Function
• Manufacturer: ATMEL Corporation

4.4.2
4.4.2.1
4.4.2.2
16
ATA6020N
Oscillator Circuits and External Clock Input Stage
RC-oscillator 1 Fully Integrated
External Input Clock
Table 4-4.
The clock module generates two output clocks. One is the system clock (SYSCL) and the other
the periphery (SUBCL). The SYSCL can supply the core and the peripherals and the SUBCL
can supply only the peripherals with clocks. The modes for clock sources are programmable
with the OS1-bit and OS0-bit in the SC-register and the CCS-bit in the CM-register.
The ATA6020N consists of two different internal RC-oscillators and one external clock input
stage.
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
selected by default after power-on reset.
Figure 4-13. RC-oscillator 1
The OSC1 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 fails and CCS = 0 is
set in the CM-register, the supervisory circuit generates a hardware reset. The input clock has
failed if the frequency is less than 500 kHz for more than 1 ms.
Mode
1
2
OS1
1
0
Clock Modes
OS0
1
1
RC-oscillator 1
RC-oscillator 1
(internal)
(internal)
CCS = 1
RC-oscillator 1
Clock Source for SYSCL
Control
RcOut1
Stop
RC-oscillator 2 with external
External input clock
trimming resistor
O
Osc-Stop
RcOut1
CCS = 0
4.0 MHz The RC-oscillator 1 is
4708D–4BMCU–09/05
Clock Source
for SUBCL
C
C
in
in
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