Product manual
XStream‐PKG‐R™RS‐232/485RFModem–ProductManualv4.2B
©2005MaxStream,Inc.Confidential&Proprietary 27
HT (Time before Wake-up Initializer) Command
<<Sleep (Low Power)> If any modems within
range are running in a “Cyclic Sleep” setting, a
wake-up initializer must be used by the
transmitting modem for sleeping modems to
remain awake [refer to the LH (“Wake-up
Initializer Timer”) Command]. When a receiving
modem in Cyclic Sleep wakes, it must detect the
wake-up initializer in order to remain awake and
receive data. The value of HT Parameter tells the
transmitter, “After a period of inactivity (no
transmitting or receiving) lasting HT amount of
time, send a long wake-up initializer”. HT
Parameter should be set to match the inactivity timeout [specified by ST (Time before Sleep)
Command] used by the receiver(s).
AT Command: ATHT
Binary Command: 0x03 (3 decimal)
Parameter Range: 0 – 0xFFFF
[x 100 milliseconds]
Default Parameter Value: 0xFFFF (means that
long wake-up initializer will not be sent)
Number of bytes returned: 2
Related Commands: LH (Wake-up Initializer
Timer), SM (Sleep Mode), ST (Time before
Sleep)
From the receiving modem perspective, after HT time elapses and the inactivity timeout [ST
Command] is met, the receiver goes into cyclic sleep. In cyclic sleep, the receiver wakes once per
sleep interval to check for a wake-up initializer. When a wake-up initializer is detected, the
modem will stay awake to receive data. The wake-up initializer must be longer than the cyclic
sleep interval to ensure that sleeping modems detect incoming data. When HT time elapses, the
transmitter then knows that it needs to send a long Wake-up Initializer for all receivers to be able
to remain awake and receive the next transmission. Matching HT to the time specified by ST on
the receiving modem guarantees that all receivers will detect the next transmission.
ID (Modem VID) Command
AT Command: ATID
Binary Command: 0x27 (39 decimal)
Parameter Range (user-settable):
0x10 - 0x7FFFF
(Factory-set and read-only) :
0x8000 – 0xFFFF
Number of bytes returned: 2
Minimum Firmware Version Required: 4.2B
(Previous versions did not support user-
settable VIDs)
<Networking> Set/Read the “Vendor
Identification Number”. Only modems with
matching IDs can communicate with each other.
Modules with non-matching VIDs will not receive
unintended data transmission.
LH (Wake-up Initializer Timer) Command
<Sleep (Low Power)> LH Command adjusts the
duration of time for which the RF initializer is
sent. When receiving modems are put into Cyclic
Sleep Mode, they power-down after a period of
inactivity [specified by ST (Time before Sleep)
Command] and will periodically awaken and listen
for transmitted data. In order for the receiving
modems to remain awake, they must detect
~35ms of the wake-up initializer.
LH Command must be used whenever a receiver
is operating in Cyclic Sleep Mode. This lengthens the Wake-up Initializer to a specific amount of
time (in tenths of a second). The Wake-up Initializer Time must be longer than the cyclic sleep
time that is determined by SM (Sleep Mode) Command. If the wake-up initializer time were less
than the Cyclic Sleep interval, the connection would be at risk of missing the wake-up initializer
transmission.
AT Command: ATLH
Binary Command: 0x0C (12 decimal)
Parameter Range: 0 – 0xFF
[x 100 milliseconds]
Default Parameter Value: 1
Number of bytes returned: 1
Related Commands: HT (Time before Wake-up
Initializer), SM (Sleep Mode), ST (Time before
Sleep)
Refer to Figures 4.3 & 4.4 of the SM Command description to view diagrams of correct and
incorrect configurations. The images help visualize the importance that the value of LH be greater
than the value of SM.