SAM4SD16B datasheet(28/67 Pages) ATMEL

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11100BS–ATARM–31-Jul-12

SAM4S Series [Preliminary]

6.3

Test Pin

The TST pin is used for JTAG Boundary Scan Manufacturing Test or Fast Flash programming

mode of the SAM4S series. The TST pin integrates a permanent pull-down resistor of about 15

Ω to GND, so that it can be left unconnected for normal operations. To enter fast programming

mode, see the Fast Flash Programming Interface (FFPI) section. For more details on the manu-

facturing and test mode, refer to the “Debug and Test” section of the product datasheet.

6.4

NRST Pin

The NRST pin is bidirectional. It is handled by the on-chip reset controller and can be driven low

to provide a reset signal to the external components or asserted low externally to reset the

microcontroller. It will reset the Core and the peripherals except the Backup region (RTC, RTT

and Supply Controller). There is no constraint on the length of the reset pulse and the reset con-

troller can guarantee a minimum pulse length. The NRST pin integrates a permanent pull-up

resistor to VDDIO of about 100 k

Ω. By default, the NRST pin is configured as an input.

6.5

ERASE Pin

The ERASE pin is used to reinitialize the Flash content (and some of its NVM bits) to an erased

state (all bits read as logic level 1). It integrates a pull-down resistor of about 100 k

Ω to GND, so

that it can be left unconnected for normal operations.

This pin is debounced by SCLK to improve the glitch tolerance. When the ERASE pin is tied high

during less than 100 ms, it is not taken into account. The pin must be tied high during more than

220 ms to perform a Flash erase operation.

The ERASE pin is a system I/O pin and can be used as a standard I/O. At startup, the ERASE

pin is not configured as a PIO pin. If the ERASE pin is used as a standard I/O, startup level of

this pin must be low to prevent unwanted erasing. Refer to Section 10.16 “Peripheral Signal Mul-

tiplexing on I/O Lines” on page 48. Also, if the ERASE pin is used as a standard I/O output,

asserting the pin to low does not erase the Flash.

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