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XStream-PKG-R™ RS-232/485 RF Modem – Product Manual v5.x00

3.2.3. Receive Mode

If the modem detects RF data while in Idle Mode, the modem transitions into Receive Mode to

receive RF packets. Once a packet is received, the modem checks the CRC to ensure that the

data was transmitted without error. If the CRC data bits on the incoming packet are invalid, the

packet is discarded. If the CRC is valid, the packet proceeds to the DO Buffer.

The modem returns to Idle Mode when valid RF data is no longer detected or after an error is

detected in the received RF data.

Figure 3.6. Data Reception Sequence

Refer to the Addressing section (p41) of the

RF Communication Modes chapter for more information

regarding address recognition.

3.2.4. Sleep Modes

Sleep Modes enable the XStream Modem to operate at minimal power consumption when not in

use. Three Sleep Mode options are available:

• Pin Sleep (Host Controlled)

• Serial Port Sleep (Wake on Serial Port activity)

• Cyclic Sleep (Wake on RF activity)

For the modem to transition into Sleep Mode, the modem must have a non-zero SM (Sleep Mode)

parameter and one of the following must occur:

1. The modem is idle (no data transmission or reception) for a user-defined period of time

(Refer to the ST (Time before Sleep) command).

2. SLEEP pin is asserted (only for Pin Sleep option).

In Sleep Mode, the modem will not transmit or receive data until the modem first transitions to

Idle Mode. All Sleep Modes are enabled and disabled using SM Command. Transitions into and

out of Sleep Modes are triggered by various mechanisms as shown in the table below.

Table 3.2. Summary of Sleep Mode Configurations

Sleep Mode

Setting

Transition into

Sleep Mode

Transition out of

Sleep Mode

Commands

Typical Power

Consumption

Pin Sleep

(SM = 1)

A microcontroller can shut down and wake

modems by asserting (high) SLEEP pin.

Note: The modem will complete a

transmission or reception before activating

Pin Sleep.

De-assert SLEEP pin. SM 6 mA

Serial Port Sleep

(SM = 2)

Automatic transition to Sleep Mode occurs

after a user-defined period of inactivity (no

transmitting or receiving of data). The

period of activity is defined using the ST

(Time before Sleep) Command.

When serial byte is

received on the DI pin.

SM, ST 25 mA

Cyclic Sleep

(SM = 3-8)

Automatic transition to Sleep Mode occurs

in cycles as defined by the SM (Sleep

Mode) Command.

Note: The cyclic sleep time interval must be

shorter than the “Wake-up Initializer Timer”

(set by LH Command).

After the cyclic sleep

time interval elapses.

Note: Modem can be

forced into Idle Mode

if PW (Pin Wake-up)

Command is issued.

SM, ST, HT, LH,

6 mA

when sleeping

For more information about Sleep Modes, refer to the individual commands listed in “Related Commands”

column of the table. The SM command is central to all Sleep Mode configurations.

Note: If serial data exists in the DI buffer while the modem is in

Receive Mode, the UART data will be transmitted after the modem is

finished receiving the RF data and has returned to Idle Mode.