Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
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5.7 Wake-up Sources
The wake-up events allow the device to exit the backup mode. When a wake-up event is detected, the Supply
Controller performs a sequence which automatically reenables the core power supply. See Figure 16-7, "Wake Up
Source" on page 277.
5.8 Fast Startup
The SAM3X/A series allows the processor to restart in a few microseconds while the processor is in wait mode. A
fast start up can occur upon detection of a low level on one of the 19 wake-up inputs (WKUP0–15 + RTC + RTT +
USB).
The fast restart circuitry (shown in Figure 28-4, "Fast Startup Circuitry" on page 530) is fully asynchronous and
provides a fast startup signal to the Power Management Controller. As soon as the fast startup signal is asserted,
the PMC automatically restarts the embedded 4/8/12 MHz fast RC oscillator, switches the master clock on this
4 MHz clock by default and reenables the processor clock.
6. Input/Output Lines
The SAM3X/A has different kinds of input/output (I/O) lines, such as general purpose I/Os (GPIO) and system
I/Os. GPIOs can have alternate functions thanks to multiplexing capabilities of the PIO controllers. The same PIO
line can be used whether in IO mode or by the multiplexed peripheral. System I/Os include pins such as test pins,
oscillators, erase or analog inputs.
With a few exceptions, the I/Os have input Schmitt triggers. Refer to the footnotes associated with PIOA to PIOF
on page 12, at the end of Table 3-1 “Signal Description List”.
6.1 General Purpose I/O Lines (GPIO)
GPIO Lines are managed by PIO Controllers. All I/Os have several input or output modes such as pull-up, input
Schmitt triggers, multi-drive (open-drain), glitch filters, debouncing or input change interrupt. Programming of these
modes is performed independently for each I/O line through the PIO controller user interface. For more details,
refer to Section 31. “Parallel Input/Output Controller (PIO)”.
The input output buffers of the PIO lines are supplied through VDDIO power supply rail.
The SAM3X/A embeds high speed pads able to handle up to 65 MHz for HSMCI and SPI clock lines and 45 MHz
on other lines. See Section 45.10 “AC Characteristics” for more details. Typical pull-up value is 100 kΩ for all I/Os.
Each I/O line also embeds an ODT (On-Die Termination) (see Figure 6-1). ODT consists of an internal series
resistor termination scheme for impedance matching between the driver output (SAM3) and the PCB track
impedance preventing signal reflection. The series resistor helps to reduce IOs switching current (di/dt) thereby
reducing in turn, EMI. It also decreases overshoot and undershoot (ringing) due to inductance of interconnect
between devices or between boards. In conclusion, ODT helps reducing signal integrity issues.
Figure 6-1. On-Die Termination
PCB Track
Z0 ~ 50 Ω
Receiver
SAM3 Driver with
R
ODT
Z
O
~ 10 Ω
Z0 ~ Z
O
+ R
ODT
ODT
36 Ω Typ.