Atmel SAM4S Xplained Pro Starter and Evaluation Kit ATSAM4S-XPRO ATSAM4S-XPRO Ficha De Dados
Códigos do produto
ATSAM4S-XPRO
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
500
It can be disabled via the XTALSEL bit in the Supply Controller Control Register (SUPC_CR).
28.4.2 Slow Clock Crystal Oscillator
The Clock Generator integrates a 32768 Hz low-power oscillator. To use this oscillator, the XIN32 and XOUT32
More details are given in the section “DC Characteristics” of the product datasheet.
Note that the user is not obliged to use the slow clock crystal and can use the RC oscillator instead.
Note that the user is not obliged to use the slow clock crystal and can use the RC oscillator instead.
Figure 28-2.
Typical Slow Clock Crystal Oscillator Connection
The user can select the crystal oscillator to be the source of the slow clock, as it provides a more accurate
frequency. The command is made by writing the Supply Controller Control Register (SUPC_CR) with the
XTALSEL bit at 1. This results in a sequence which first configures the PIO lines multiplexed with XIN32 and
XOUT32 to be driven by the oscillator, then enables the crystal oscillator and then disables the RC oscillator to
save power. The switch of the slow clock source is glitch free. The OSCSEL bit of the Supply Controller Status
Register (SUPC_SR) or the OSCSEL bit of the PMC Status Register (PMC_SR) tracks the oscillator frequency
downstream. It must be read in order to be informed when the switch sequence, initiated when a new value is
written in the XTALSEL bit of SUPC_CR, is done.
Coming back on the RC oscillator is only possible by shutting down the VDDIO power supply. If the user does not
Coming back on the RC oscillator is only possible by shutting down the VDDIO power supply. If the user does not
need the crystal oscillator, the XIN32 and XOUT32 pins can be left unconnected since by default the XIN32 and
XOUT32 system I/O pins are in PIO input mode with pull-up after reset.
The user can also set the crystal oscillator in bypass mode instead of connecting a crystal. In this case, the user
The user can also set the crystal oscillator in bypass mode instead of connecting a crystal. In this case, the user
has to provide the external clock signal on XIN32. The input characteristics of the XIN32 pin are given in the
product electrical characteristics section. In order to set the bypass mode, the OSCBYPASS bit of the Supply
Controller Mode Register (SUPC_MR) needs to be set at 1.
the user can set the slow clock crystal oscillator in bypass mode instead of connecting a crystal. In this case, the
the user can set the slow clock crystal oscillator in bypass mode instead of connecting a crystal. In this case, the
user has to provide the external clock signal on XIN32. The input characteristics of the XIN32 pin under these
conditions are given in the product electrical characteristics section.
The programmer has to be sure to set the OSCBYPASS bit in the Supply Controller Mode Register (SUPC_MR)
The programmer has to be sure to set the OSCBYPASS bit in the Supply Controller Mode Register (SUPC_MR)
and XTALSEL bit in the Supply Controller Control Register (SUPC_CR).
XIN32
XOUT32
GND
32768 Hz
Crystal