TRM-915-R250 datasheet(8/39 Pages) LINX

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Low-Power States

The module supports three power saving modes: Standby, Sleep and Deep

Sleep. Standby and Sleep are included primarily for legacy compatibility

with DTS and EUR Series modules. The hardware required to support

these two low-power modes fully is not present in the 25 Series modules.

As a result, the current consumption in these two modes is considerably

higher than their DTS / EUR counterparts. It is recommended that

applications utilize the Deep Sleep mode for power savings.

In the Sleep and Deep Sleep modes, the transceiver is powered down

and does not synchronize with other modules. Sleep mode draws more

current than Deep Sleep mode. In Deep Sleep mode the module draws the

least current. To wake the module up from this mode the RESET line must

be held low for at least 20µs and then taken high. The module does not

monitor the receive channel in either mode. Therefore, a sleeping module

cannot be woken through the RF interface.

If regACKONWAKE is enabled, the module transmits a 0x06 character on

the TXD line once awakened from a low-power mode or power-off state.

This indicates that the module is ready to resume operations.

Figure 8 indicates the line states while in a low-power mode.

250 Series Transceiver Low-Power Line States

Line Name

Pin Number Pin State

PR_PKT

Driven low

TXD

Input with weak pull-up

RESET

Input with weak pull-up

C2D

Input with weak pull-up

CMD_RSP

Input with weak pull-up

Driven low

RSSI

Driven low

CMD

Input with weak pull-up

CTS

In Standby, Sleep: Driven Low, In Deep Sleep: Driven High

RXD

Input with weak pull-up

Figure 8: 250 Series Transceiver Low-Power Line States

Standby

Standby is selected by writing a 0x02 to regOPMODE. In this mode,

the internal oscillator of the module’s protocol controller is lowered to its

slowest setting. The transmitter and receiver hardware is in power-down,

but the radio’s oscillator is enabled and running. The module wakes from

standby in less than 6ms. A low pulse on the RXD line wakes the module.

This pulse should be at least 1 bit-time in duration, so sending any byte to

the UART wakes it with the low start bit. Because the module’s oscillator

is not capable at running at ultra-low speeds, use of this mode is not

recommended for new applications. The RAM contents are preserved

during standby. If the RAM fails an integrity check, the module issues itself

a software reset to force re-initialization.

Sleep

Sleep is selected by writing a 0x01 to regOPMODE. The internal oscillator

of the module’s protocol controller is lowered to its slowest setting, and

all radio services are stopped (receiver, transmitter, oscillator, etc.). The

module wakes from sleep in less than 6ms. A low pulse on the RXD line

wakes the module. This pulse should be at least 1 bit-time in duration, so

sending any byte to the UART wakes it with the low start bit. Because the

module’s oscillator is not capable at running at ultra-low speeds, use of

this mode is not recommended for new applications. The RAM contents

are preserved during sleep. If the RAM fails an integrity check, the module

issues itself a software reset to force re-initialization.

Deep Sleep

Deep sleep is selected by writing a 0x03 to regOPMODE. When the

module is put into deep sleep, the CTS line is brought high to indicate that

the module is not ready to accept UART data. The radio is placed in its

lowest power mode and all services are stopped. The protocol controller’s

oscillator is also stopped and all non-essential functions are turned off.

While powered, this mode consumes the least amount of current. The

module wakes from deep sleep in less than 6ms. A low pulse of at least

20µs on the RESET line starts the waking process, but the module doesn’t

begin executing wake instructions until the RESET line is returned high.

As with the other low-power modes, the RAM contents are preserved.

If the RAM fails an integrity check, the module issues itself a software

reset to force re-initialization. Note that, if the volatile data rate register is

changed during the host application initialization (regUARTDATARATE),

the re-initialization returns the module to the value in the non-volatile

counterpart (regNVUSERDATARATE).

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