
188
42073A-MCU Wireless-02/13
ATmega2564/1284/644RFR2
12.4.6 Port Pins
When entering a sleep mode, all port pins should be configured to use minimum power.
The most important is then to ensure that no pins drive resistive loads. In sleep modes
where both the I/O clock (clkI/O) and the ADC clock (clkADC) are stopped, the input
buffers of the device will be disabled. This ensures that no power is consumed by the
input logic when not needed. In some cases, the input logic is needed for detecting
217 for details on which pins are enabled. If the input buffer is enabled and the input
signal is left floating or have an analog signal level close to DEVDD/2, the input buffer
will use excessive power.
For analog input pins, the digital input buffer should be disabled at all times. An analog
signal level close to DEVDD/2 on an input pin can cause significant current even in
active mode. Digital input buffers can be disabled by writing to the Digital Input Disable
12.4.7 On-chip Debug System
If the On-chip debug system is enabled by the OCDEN Fuse and the chip enters sleep
mode, the main clock source is enabled, and hence, always consumes power. In the
deeper sleep modes, this will contribute significantly to the total current consumption.
There are three alternative ways to disable the OCD system:
Disable the OCDEN Fuse.
Disable the JTAGEN Fuse.
Write one to the JTD bit in MCUCR.
12.4.8 Symbol Counter
The Symbol Counter acts as a separate counter, which uses either the 16MHz clock
from XTAL1/XTAL2 crystal pins or the clock from PG3/PG4 low frequency crystal pins.
If the Symbol Counter module is not used, it should be disabled, see section
"MAC12.4.9 Radio Transceiver
The radio transceiver module is automatically starting its state machine after power on.
While the CPU is in any sleep mode, the radio transceiver remains active. This enables
the radio transceiver to wakeup the MCU if a pending action is over (frame received or
transmission completed). The radio transceiver will be inactive during sleep, if either the
its power reduction bit PRTRX24 in register PRR1 is set or it is send into SLEEP mode,
the 16MHz crystal oscillator is started first and afterwards the radio transceiver with
TRX_OFF state.
The radio transceiver is derived from a stand alone solution that was partly controlled
by external pins. Now the radio transceiver is fully controlled by individual register bits.
The radio transceiver has a separate reset signal. A radio transceiver reset is initiated
by setting bit TRXRST in register TRXPR. This bit is self-resetting.
The radio transceiver signal SLPTR can be controlled by the bit SLPTR in register
TRXPR and is used to set the radio transceiver into SLEEP mode (assuming
TRX_STATE is TRX_OFF). This bit has a multiple function, see section
"Low-Power 2.4