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RL56CSM/3

AnyPort™ Multi-Service Access Processor

Conexant Systems 

RL56CSMV/3 and RL56CSM/3 Hardware Interface Description

1.3 TECHNICAL OVERVIEW

1.3.1 General Description

The CSMV/3 provides the processing core for three channels of a central site Remote Access Server supporting high speed

T1/E1/PRI digital lines. The OEM adds two oscillators, SDRAM, and discrete components to complete the Multi-Service

Access Processor system.

The access processor includes a full-featured, self-contained data/fax/Voice modem solution shown in Figure 1-1. Data

modem handshake, fax modem protocol, voice codecs, and ISDN data connection functions are supported and controlled

through the AT command set.

1.3.2 Digital Data Pump (DDP)

The DDP is a +3.3V CONEXANT data pump supporting PSTN data/fax modem operation, ISDN B Channel call termination

mode, and voice coding/decoding. The DDP executes internal code including downloadable modules from on-chip memory.

Digital data transfers serially between the T1/E1 framer device and the DDP at a data rate up to 8.192 Mbps. The T1/E1

framing device provides a strobe signal and the DDP TSA logic detects where the data for the channel starts in the serial

TDM data stream using a programmable counter. The DDP performs PCM µ-law or A-law conversion and synchronizes with

an external network clock.

1.3.3 ARM Microcontroller (MCU)

The ARM MCU performs the command processing and interfaces to the central site system controller via a 16-bit parallel host

interface. Two 64-word deep FIFOs are used for improved data throughput between the access processor and system

controller. This single powerful RISC processor controls three separate channels. A SDRAM loader is available to support

download from the central site system controller on startup, if desired.

1.3.4 Access Processor Operation

In data modem modes, each channel can independently connect to PSTN data modems at rates up to 56 kbps or ISDN

terminal adapters at rates up to 64 kbps. A downloadable architecture allows for software download. For PSTN modems,

complete handshake and data rate negotiations are performed. By optimizing the modem configuration for line conditions, the

DDP can connect at the highest data rate that the channel can support from 56 kbps to 300 bps with automatic fallback.

Automode operation in V.34 is provided in accordance with PN3320 and in V.32 bis in accordance with PN2330. All tone and

pattern detection functions required by the applicable ITU or Bell standard are supported. Asynchronous to synchronous

conversion is supported inside the controller to ease PPP processing in PSTN data mode.

When the remote end is an ISDN terminal adapter, the CSMV/3 provides HDLC control including HDLC Flag

generation/detection, bit stuffing/extraction, and CRC generation/checking. V.120, V.110, and LAP-B X.75 are also supported.

V.120 is a standard for encapsulating asynchronous data communications traffic into ISDN data streams.

In fax modem mode, the CSMV/3 supports Group 3 facsimile send and receive speeds of 14400, 12000, 9600, 7200, 4800,

and 2400 bps. Fax modem modes support T.30 fax requirements. Fax data transmission and reception performed by the

access processor are controlled and monitored through the EIA-578 Class 1 and Class 2 command interface. Both transmit

and receive fax data are buffered within the access processor.

In Voice mode, the CSMV/3 encodes PCM audio data from the line into Real-Time Protocol (RTP) packets for the Host, and

decodes RTP packets from the Host, to output PCM audio data to the line. In Voice mode, DTMF digits can be detected and

transmitted, and a Voice Activity Detector can be enabled.

1.3.5 Access Processor Firmware

Access processor firmware performs processing of general modem control, command sets, error correction and data

compression, fax class 1 and class 2, voice coding and decoding (optional), and central site system controller interface

functions.

The firmware is provided in object code form for executing from external SDRAM after download on startup using the ROM-

coded Boot Loader. Equipment designers can add their own functions in firmware using commonly available development

tools and the C programming language.

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