Atmel Evaluation Kit for the SAM4E Series of Flash Microcontrollers ATSAM4E-EK ATSAM4E-EK Data Sheet
Product codes
ATSAM4E-EK
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
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6.
Input/Output Lines
The SAM4E 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.
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.
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 an alternate function as analog input. When a GPIO is set in analog mode, all digital
features of the I/O are disabled.
features of the I/O are disabled.
The input/output buffers of the PIO lines are supplied through VDDIO power supply rail.
The SAM4E device embeds high speed pads able. See “AC Characteristics” section of the datasheet for more
details. Typical pull-up and pull-down value is 100 k
details. Typical pull-up and pull-down value is 100 k
Ω for all I/Os.
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 (SAM4E) 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.
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
PCB Trace
Z0 ~ 50 ohms
Receiver
SAM4 Driver with
Rodt
Zout ~ 10 ohms
Z0 ~ Zout + Rodt
ODT
36 ohms Typ.