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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
13.4
Functional Description
13.4.1
Reset Controller Overview
The Reset Controller is made up of an NRST Manager and a Reset State Manager. It runs at
Slow Clock and generates the following reset signals:
• proc_nreset: Processor reset line. It also resets the Watchdog Timer
• periph_nreset: Affects the whole set of embedded peripherals
• nrst_out: Drives the NRST pin
These reset signals are asserted by the Reset Controller, either on external events or on soft-
ware action. The Reset State Manager controls the generation of reset signals and provides a
signal to the NRST Manager when an assertion of the NRST pin is required.
The NRST Manager shapes the NRST assertion during a programmable time, thus controlling
external device resets.
The Reset Controller Mode Register (RSTC_MR), allowing the configuration of the Reset Con-
troller, is powered with VDDIO, so that its configuration is saved as long as VDDIO is on.
13.4.2
NRST Manager
After power-up, NRST is an output during the ERSTL time period defined in the RSTC_MR.
When ERSTL has elapsed, the pin behaves as an input and all the system is held in reset if
NRST is tied to GND by an external signal.
The NRST Manager samples the NRST input pin and drives this pin low when required by the
Reset State Manager.
shows the block diagram of the NRST Manager.
Figure 13-2. NRST Manager
13.4.2.1
NRST Signal or Interrupt
The NRST Manager samples the NRST pin at Slow Clock speed. When the line is detected low,
a User Reset is reported to the Reset State Manager.
However, the NRST Manager can be programmed to not trigger a reset when an assertion of
NRST occurs. Writing the bit URSTEN at 0 in RSTC_MR disables the User Reset trigger.
External Reset Timer
URSTS
URSTEN
ERSTL
exter_nreset
URSTIEN
RSTC_MR
RSTC_MR
RSTC_MR
RSTC_SR
NRSTL
nrst_out
NRST
rstc_irq
Other
interrupt
sources
user_reset
Содержание SAM4S Series
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