Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet
Product codes
ATSAM4S-WPIR-RD
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
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6.
Input/Output Lines
The SAM4S has several kinds of input/output (I/O) lines such as general purpose I/Os (GPIO) and system I/Os.
GPIOs can have alternate functionality due to multiplexing capabilities of the PIO controllers. The same PIO line
can be used whether in I/O mode or by the multiplexed peripheral. System I/Os include pins such as test pins,
oscillators, erase or analog inputs.
6.1
General Purpose I/O Lines
GPIO Lines are managed by PIO controllers. All I/Os have several input or output modes such as pull-up or pull-
down, 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 the product “PIO Controller” section.
Some GPIOs can have alternate function as analog input. When the GPIO is set in analog mode, all digital
Some GPIOs can have alternate function as analog input. When the GPIO is set in analog mode, all digital
features of the I/O are disabled.
The input/output buffers of the PIO lines are supplied through VDDIO power supply rail.
The SAM4S embeds high-speed pads able to handle up to 70 MHz for HSMCI (MCK/2), 70 MHz for SPI clock
The input/output buffers of the PIO lines are supplied through VDDIO power supply rail.
The SAM4S embeds high-speed pads able to handle up to 70 MHz for HSMCI (MCK/2), 70 MHz for SPI clock
lines and 46 MHz on other lines. See the AC Characteristics section of the electrical characteristics. Typical pull-up
and pull-down value is 100 kΩ for all I/Os.
Each I/O line also embeds an ODT (On-Die Termination), (see
Each I/O line also embeds an ODT (On-Die Termination), (see
below). It consists of an internal series
resistor termination scheme for impedance matching between the driver output (SAM4S) and the PCB trace
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 diminish signal integrity issues.
Figure 6-1.
On-Die Termination
6.2
System I/O Lines
System I/O lines are pins used by oscillators, test mode, reset and JTAG.
provides the SAM4S system
I/O lines shared with PIO lines.
These pins are software configurable as general-purpose I/O or system pins. At startup, the default function of
These pins are software configurable as general-purpose I/O or system pins. At startup, the default function of
these pins is always used.
Notes: 1. If PB12 is used as PIO input in user applications, a low level must be ensured at startup to prevent Flash erase before the
user application sets PB12 into PIO mode,
2. Refer to the section “Slow Clock Generator” of the “Supply Controller (SUPC)”.
3. Refer to the section “3 to 20 MHZ Crystal Oscillator” of the “Power Management Controller (PMC)”.
3. Refer to the section “3 to 20 MHZ Crystal Oscillator” of the “Power Management Controller (PMC)”.
PCB Trace
Z0 ~ 50 Ohms
Receiver
SAM4 Driver with
Rodt
Zout ~ 10 Ohms
Z0 ~ Zout + Rodt
ODT
36 Ohms Typ.