User's Guide

User’s Guide CDPD Operation
2110059 Rev 1.1 Proprietary and Confidential Page 39
If logic sleep is enabled (S31 > 0), it will automatically engage on the next CDPD sleep mode
interval. Logic sleep continues until data or an AT command is received from the host, or the
modem must perform the periodic CDPD sleep mode check. After performing the periodic
network check, and provided there is no pending AT command or traffic from the host, the modem
will resume both CDPD and logic sleep.
The modem can use logic sleep while in auto-answer mode. The modem logic must wake-up
periodically as part of the CDPD sleep operation to check the network for messages. Incoming
data from the network amounts to a RING when auto-answer is enabled, so the modem logic will
be awake to receive messages.
This feature is controlled with register S31 (Logic Sleep). Setting the register to 0 (zero) will
disable logic sleep. Setting it to 1 will enable normal logic sleep. In this condition the modem
will reduce power until the host sends a command or CDPD sleep operation requires activity. It
will wake as soon as a character arrives from the host, or automatically as needed to make periodic
network checks for traffic.
Logic Deep Sleep
Setting the Logic Sleep register to 2 will enable deep-sleep. This will cause the modem to shut
down even more hardware, conserving even more power. The disadvantage to this is that the
modem will lose the first incoming character(s) from the host (DTE). In fact, the modem will take
80 milliseconds, from the start of the first incoming character, to wake up. The host should send a
“dummy” character first, which the modem will lose, and then wait the 80ms delay before sending
the complete command or data string. Automatic wake-ups to check the network will still occur
so no incoming network traffic is lost.
5.6. Friends Only
Friends Only is a feature available when either the UDP or TCP PAD is enabled in a server
session, but is not used with the SLIP protocol.
Friends Only permits reception of packets to be restricted (for security reasons) to a predefined
group of IP addresses (friends). Friends Only mode is controlled by entering IP addresses in a
Friend Only table. If the table is not empty, the feature is enabled and the comparison of packet
source addresses against the list stored in the modem will be made.
This subject is discussed in further detail in both the UDP and TCP packet services sections
below.
5.7. Dial Directory
A supplemental application of the Friends Only list is to “quick dial” client sessions to addresses
on the list. The list supports the entry of a port number along with each IP. The port number is
ignored by server sessions when testing incoming packets but is used for quick dialling.
The Dial command (D) supports use of a digit parameter (1 – 10) in place of an explicit IP and
port. The number is the index to an entry in the Friends Only list. Provided the entry contains a
valid IP and port, the modem will dial that destination to connect a client session.
5.8. Packet Services
SB300 Series modems support three connection protocols in CDPD:
• SLIP
• UDP PAD
• TCP PAD
PPP service is not yet implemented but will be included in a future firmware release.