EM260-RTR datasheet(21/50 Pages) SILICONIMAGE

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EM260

Page 21

120-0260-000M Rev 1.1

EmberZNet PRO stack utilizes these random numbers to seed the Random MAC Backoff and Encryption Key

Generators.

4.13 Watchdog Timer

The EM260 contains an internal watchdog timer clocked from the internal oscillator. If the timer reaches its

time-out value of approximately 2 seconds, it will reset the EM260. This reset signal cannot be routed

externally to the Host.

The EM260 firmware will periodically restart the watchdog timer while the firmware is running normally. The

Host cannot effect or configure the watchdog timer.

4.14 Sleep Timer

The 16-bit sleep timer is contained in the always-powered digital block. The clock source for the sleep timer

is a calibrated 1kHz clock. The frequency is slowed down with a 2N prescaler to generate a final timer

resolution of 1ms. With a 1ms tick and a 16-bit timer, the timer wraps about every 65.5 seconds. The

EmberZNet PRO stack appropriately handles timer wraps allowing the Host to order a theoretical maximum

sleep delay of 4 million seconds.

4.15 Power Management

The EM260 supports four different power modes: active, idle, deep sleep, and power down.

Active mode is the normal, operating state of the EM260.

While in idle mode, code execution halts until any interrupt occurs. All modules of the EM260 including the

radio continue to operate normally. The EmberZNet PRO stack automatically invokes idle as appropriate.

Deep sleep mode and power down mode both power off most of the EM260, including the radio, and leave only

the critical chip functions powered. The internal regulator is disabled and VREG_OUT is turned off. All output

signals are maintained in a frozen state. Upon waking from deep sleep or power down mode, the internal

regulator is re-enabled. Deep sleep and power down result in the same sleep current consumption. The two

sleep modes differ as follows: the EM260 can wake on both an internal timer and an external signal from deep

sleep mode; power down mode can only wake on an external signal.

EM260-RTR Datasheet(PDF) 21 Page - Silicon image