Bt8954

Features:

• Voice Pair Gain Framer
  Frames and transports PCM data streams over 1218,000 ft. (3.75.5 km) distances when coupled with Bt8960 or Bt8970
• PCM Interface
  Supports popular PCM codecs
  Programmable payload to support 218 64 kbps voice channels
  2.048, 1.536 MHz PCM reference clock generation
  6.144, 8.192, 20.48 MHz ADPCM reference clock generation
• DSL Interface
  Connects to Bt8960 or Bt8970
  Supports 1601168 kbps bit rates
  Error performance monitoring
  Auto tip/ring reversal
• Microcomputer Interface
  Glueless interface to Intel 8051 and Motorola 68302 processors
  Access to overhead and signaling registers
• Supports ADPCM codecs (32 kbps)
• PCM and DSL loopbacks
• CMOS technology, 5 V operation
• Low-power operation
  Enables compatibility with line-powered systems
• 68-pin PLCC
• JTAG/IEEE Std 1149.1-1990
• 40 °C to +85 °C operation


Application

• Voice Pair Gain Systems (Clear)
  PCM2, PCM4(PCM1+3), PCM6,
  PCM8, PCM10/11, PCM12, PCM18
• ADPCM Voice Pair Gain Systems (Compressed)
  ADPCM12, ADPCM24, ADPCM36


Pinout




Specifications

Symbol	Parameter	Minimum	Maximum	Units
VDD	Supply Voltage	0.3	7	V
VI	Voltage on Any Signal Pin	1.0	VDD+0.3	V
TST	Storage Temperature	40	125	°C
TVSOL	Vapor Phase Soldering Temperature (1 minute)	-	220	°C
JA	Thermal Resistance (68 PLCC), Still Air	-	39.8	°C/W
NOTE(S): Stresses greater than those listed in this table may cause permanent damage to the device. This is a stress rating only. Functional operation of the device at these or any other conditions beyond those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Description

The Bt8954 framer has been tailored specifically to meet the needs of voice pair gain systems (also referred to as "cable relief systems" and "digital subscriber line carriers") by providing a direct connection to the DSL modem and the CODEC. It performs data, clock, and format conversions necessary to construct a Pulse Code Multiplexed (PCM) channel from a Symmetrical Digital Subscriber Line (SDSL) or a High-Bit-Rate Digital Subscriber Line (HDSL) channel. The PCM channel consists of transmit and receive data, clock, and frame sync signals configured for 218 voice channels. The PCM channel connects directly to popular PCM codecs. The Digital Subscriber Line (DSL) channel interface consists of serial data and clock connected to a RS8973, Bt8970 or a Bt8960 DSL Transceiver. The Bt8954 supports clear and compressed voice system. When coupled with a Bt8960, the Bt8954 provides PCM4 functions at greater than 5 km reach with no voice compression, allowing V.34 modem operation.

At one end, Bt8954 multiplexes payload data from several PCM codecs with the appropriate overhead and signaling bits into one transport frame that is passed on to the bit-pump, for transport over a single twisted pair. At the other end, Bt8954 demultiplexes the DSL bit stream into payload data sent to the PCM codec, and overhead data written into microcomputer-accessible registers.

Embedded Operations Channel (EOC) and signaling overhead can be inserted via the Microcomputer Interface (MCI). Control and status registers of Bt8954  are accessed via the MCI. One common register group configures the PCM interface formatter, Phase-Locked Loop (PLL), and PCM Loopback (LB). Another group of DSL channel registers configures the elastic store FIFOs, overhead muxes, receive framer, payload mapper, and the DSL loopback. Status registers monitor  of Bt8954 received overhead, PLL, FIFO, and framer operations, including CRC and FEBE error counts.