HP X09 Manual download pdf (Page 47)

XStream‐PKG‐E™EthernetRFModem–ProductManualv5.x00[2006.02.24]

©2006MaxStream,Inc.ConfidentialandProprietary 47

Initiating a Connection

Connection Guidelines:

• A remote modem can only request a connection with the base modem.

• The base modem may hold off or grant a connection request to another modem.

• A remote modem will not try to establish a connection if one already exists.

• A connection fails if no response is received after RR (Retries) CRP packets. After a failure,

whatever condition was causing a connection to be established is cleared. If the condition

was data to be sent, all data in the DI buffer will be flushed. If the condition was DI3

transition, then no connection will be attempted until another correct DI3 transition.

• A global connection cannot fail. [Definition is on next page.]

Once in Multi-Streaming Mode (MD > 0), several events can initiate an exclusive connection:

1. Remote modem has payload to transmit. After a remote modem receives data from its host,

the modem will attempt to establish a connection with the base modem. The connection is

defined by the remote’s DT (Destination Address) parameter. If another remote has a

connection with the base, no connection will be established until the connection runs its

course. Any remotes requesting a connection will then arbitrate for the next connection. RR

(Retries) and RN (Random back-off) parameters control this arbitration.

2. Base sets the DT (Destination Address) parameter. When the base modem sets the DT

(Destination Address) parameter, an exclusive connection is immediately initiated with the

remote modem that has a matching DT parameter. After the DT command is sent (If

ATCM=1), the base modem indicates a successful connection with a “CONNECT XXXX” string

where "XXXX" is the remote's address. An unsuccessful connection is indicated with an

“ERROR” string. If the connection is successful, the modem immediately exits AT Command

Mode and data can be sent to and received from the connected remote modem. If an error is

returned, the modem stays in AT Command Mode. If a base is connected to a remote when

the DT command is executed, the current connection is disconnected before a new

connection is created.

3. DI3 pin (pin 2, SLEEP) is asserted (set low). Both base and remote modems can create a

connection (defined by the current DT (Destination Address) parameter) when the DI3 pin is

asserted (driven high). DR (DI3 Configuration) Command is used to establish this mode. If a

remote asserts DI3, a connection request will be sent when no connection is active. If the

base asserts DI3, a connection will immediately be established with the remote after any

connection.

Initiating a Disconnection

To disconnect, the base modem sends a DGP (disconnect grant packet). A remote modem can

only request a disconnect. The following conditions cause a disconnect:

1. No over-the-air data sent or received for CE (Connection Inactivity Timeout) time. If no over-

the-air data is successfully sent (no acknowledgement received) or received (any good

packet) for CE time, the connection will be dropped. Only a base modem can detect this

condition. Refer to CE Command.

2. Absolute CB (Connection Duration Timeout). The CB parameter defines an absolute timeout.

A timer is started on the remote units when a connection is established. When the

connection has been active for CB time, the base will close the connection. A remote that

detects this condition will automatically disconnect (it will not send a DRP (disconnect

request packet)). Remotes that monitor a connection between the base and another remote

will disregard any connection after the CB time. Refer to CB Command.

3. DI3 pin (pin 2, SLEEP) is de-asserted (set high). A base or remote modem can cause a

disconnect by setting the DI3 line high. If no connection is active, the de-assertion is

ignored. A remote will request a disconnect if DI3 is de-asserted and the remote is currently

connected the base. Refer to DR (DI3 Configuration) Command.

4. A remote or a base modem receives the ATDC (Disconnect) Command.

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HP X09 Manual Page 47

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