CMX208 View Datasheet(PDF) - CML Microsystems Plc

Part Name

Description

Manufacturer

CMX208

ISDN Dual Telephony Protocol Engine

CML Microsystems Plc 

ISDN Dual Telephony Protocol Engine

CMX208

1.5.2 Initialisation

On power-up, the CMX208 assumes its default values, which are factory programmed into the

firmware. It then performs a self-test, during which all of the LED pins and the ILFI pin are held high

for 3s. If the test is unsuccessful, the CMX208 remains in this condition.

If the test is successful, the CMX208 reads its preset values from the attached EEPROM and

examines the state of the ISDN link (ie Layer 1) before commencing normal operation. On power-up,

the ISDN link is de-activated, the POTS ports are assumed to be on-hook and ringing is disabled.

1.5.3 ISDN Interface

Two simultaneous voice calls are possible. Incoming calls are firstly checked for other calls present,

then the MSN is checked for validity, then the channel mapping, so that responses will be handled

accordingly.

When channel mapping is enabled, outgoing calls will request the channel enabled. When not

enabled, a request for any channel is made. If no free channels are available for outgoing calls, a

locally generated busy tone is returned to the analogue port.

1.5.3.1 Activation

Activation occurs in the following circumstances:

• The ISDN network activates.

• The device connected to the analogue port goes off hook.

The Terminal Endpoint Identifier (TEI) is negotiated. Line powering of the CMX208 is not supported.

The 'AR' indicator (LED8) toggles between high and low states when the CMX208 is powered up, and

remains constantly low once the CMX208 identifies an activated ISDN line.

ISDN line power detection is not implemented and the CMX208 will negotiate a new TEI on any new

network activation.

1.5.3.2 De-activation or Line Disconnection

De-activation or line disconnection causes the TEI to be removed. Upon re-connection the CMX208

will only be re-activated and request a new TEI when one of the conditions in the above section is met.

1.5.3.3 Line Failure Detection

If the line failure detection parameter is enabled (via either POTS port) the CMX208 will check that

Layer 2 communications are active every sample period of 30 seconds. If Layer 2 communications

are not active, the CMX208 will attempt to activate them. If they remain inactive for 2 sample periods,

the line is deemed to have failed, so then the ILFI pin is set high and both RINGP1 and RINGN1 pins

(port 1 only) are set low. The CMX208 continues to attempt to activate the line and if it becomes

active and stays active for 2 sample periods, then the ILFI pin is set low and both RINGP1 and

RINGN1 pins (port 1 only) are restored to their default settings.

1.5.3.4 Incoming Calls

Incoming voice calls and calls from analogue lines are directed to the analogue ports and all other

incoming calls are rejected with a Cause Information Element set to 'Incompatible Destination'.

© 1999 Consumer Microcircuits Limited

11

© 1999 Chiron Technology Limited

D/208/1

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