CMX208S1 MX-COM, Inc., CMX208S1 Datasheet - Page 8

• Manufacturer Part Number: CMX208S1
• Description: ISDN dual telephony protocol engine
• Manufacturer: MX-COM, Inc.

ISDN Dual Telephony Protocol Engine
8
CMX208 Advance Information
4.
General Description
The CMX208 is a single-chip data processor which has been mask programmed with firmware to implement
an ISDN protocol stack. This enables the CMX208 to interface two analog (POTS) ports to an ISDN S-bus
network connection. Key variables are stored in an external EEPROM and the user can provide additional
features by adding external ROM and RAM. Access to the firmware Application Programmer's Interface (API)
facilitates the seamless integration of the user's additional features with the pre-programmed ISDN to POTS
interfaces.
The CMX208 is intended for use as part of an ISDN chipset and all descriptions in this data sheet refer to this
implementation, which is shown in Figure 3. The use of alternative chipsets is not supported.
The firmware supports connection to an ISDN S-bus network interface via the Siemens PSB21525 HDLC
controller and the AMD AM79C30 ST controller with integral PCM codec for a single POTS port. An auxiliary
Motorola MC145480 PCM codec will need to be added for the second POTS port.
The CMX208 interfaces with up to two CMX605 Tone Generator and DTMF Receiver chips, which decode
incoming DTMF tones and generate certain call progress signals (e.g. busy tone) normally originating from an
analog telephone exchange. The firmware translates the CMX605 data into ISDN D-channel commands and
vice versa to support both incoming and outgoing calls. For the ISDN interface, D-channel commands
sufficient for standard telephony applications are implemented. With the aid of a small amount of discrete
circuitry, exchange battery voltage, ringing current, line reversal and off-hook detection are also supported, to
complete the POTS interface. The CMX208 has dedicated outputs for visible indicators (LEDs) that can be
used to provide information on the call status. Support for Multiple Subscriber Numbering is also included in
the firmware.
The CMX208 can be configured by means of keypad programming via either POTS port. Configuration
parameters allow the user to change (for example) the format and cadence of the ringing signal, so as to
facilitate use of the CMX208 in different countries. Each POTS interface is able to configure the variables
relevant to its own use.
An Application Programmer's Interface (API) is available and is described separately in Section 4.6. Further
details are available on completion of a Non-Disclosure Agreement. Please contact MX-COM directly for
further details.
The firmware and finite state machine embedded in the CMX208 have been used in products that have
gained ETSI CTR3 approval.
MX-COM, Inc
2000 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC, 27105-1201, USA
Doc. # 20480214.001
www.mxcom.com tel: [phone] 744 5050 fax: [phone]
2000 Chiron Technology Limited
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