User's Guide

The Operational View SB300 Series

Page 38 Proprietary and Confidential 2110059 Rev 1.1

5.5. Sleep Mode

CDPD provides a facility to allow modems to go to “sleep” when they do not have active traffic

with the network. This allows the modems to shut down hardware to reduce power consumption.

When the modem is waiting for data from either the host or the network, it does not need to keep

all hardware systems running. The modem can negotiate with the CDPD network to have the

network send a periodic message advising if there is pending traffic. Between these messages, the

modem can be programmed to shut down the receiver (go to sleep). The modem will wake up at

the predetermined intervals to check the network for incoming traffic. If there is no pending

traffic, then the receiver can go back to sleep until the next scheduled notification message.

The SB300 Series modems can use this feature and have added an additional feature called “logic

sleep” and “logic deep sleep” to further reduce power consumption. Each of these sleep modes is

described below.

5.5.1. CDPD Sleep

This is what is meant by the general term “sleep” mode. CDPD sleep is controlled by setting

Setting the register to 0 (zero) will disable sleep mode. The modem will keep the receiver active

for immediate handling of any incoming traffic from the network or host.

Sleep is enabled by setting the register to the time in seconds, from 10 to 3600 (1 hour), during

which the modem must not have network traffic. Provided there is no traffic to or from the

network during that interval, the modem will begin using CDPD sleep.

NOTE

For CDPD sleep to engage, the modem must have negotiated with the network to allow

its use. This means that the setting of the enabling register (+WS175) must have been

done prior to network registration. If the modem has already registered with the

network, changing the setting of the CDPD Sleep Idle Time will have no effect until the

modem is de-registered and re-registered.

The CDPD network advises the modem of the time interval between periodic notification

messages. This is typically 60 to 90 seconds. You should verify with your carrier what interval is

used.

Once sleep mode is engaged, the modem logic will turn off the radio receiver. It will turn on the

receiver at the intervals prescribed by the network to check for traffic. If there is traffic, the

modem will then receive it. Should the network require a CDPD channel hop while the modem is

sleeping, the modem will have to scan for the new channel when it wakes for the next periodic

check. This is handled automatically.

The disadvantage to sleep mode is that traffic from the network will have to wait up to a

maximum of one interval for the next notification cycle before the modem can receive it. This

delay in responding can be too great for some time critical applications. This delay also applies to

“ping” packets sent to a sleeping modem.

While sleeping, the modem logic is still active and ready to receive data from the host at any time.

The modem will immediately wake up the radio for host generated traffic going out to the

network. There is no delay in sending messages, only in receiving network packets.

5.5.2. Logic Sleep

In addition to switching off the radio for CDPD sleep, the modem can be placed in a logic sleep

mode. This further reduces the power consumption of the modem. Logic sleep will not engage

unless CDPD sleep is already engaged.