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BT8110

High-Capacity ADPCM Processor

Conexant Systems 

Bt8110/8110B

High-Capacity ADPCM Processor

2.0 Functional Description

2.1 Overview

2.1.1 Clocking and Synchronization

Each operating mode of the Bt8110/8110B requires clock and synchronization

inputs to allow proper operation. If the microprocessor mode is used, then the

synchronization signal frequency can be any submultiple of a PCM frame

(8 kHz). If the hardware mode is used, then the synchronization frequency can be

any submultiple of 1/32 of the clock frequency; in this case the synchronization

signal is used to identify consecutive inputs and outputs.

The CLOCK signal must operate at a frequency of 8.192 MHz to obtain the

8 kHz frame rate for PCM signals. This clock can be gapped and may have a peak

rate of 16.5 MHz (maximum rate of 16.384 MHz is used in the E1 transcoder

application).

The SYNC signal must operate at a submultiple of the 8 kHz frame rate. The

SYNC signal is active on the falling edge; the rising edge can occur anywhere in

the frame. (In direct framer interface mode, the SYNC signal is active on the

rising edge.) The SYNC signal synchronizes internal modulo-32 counters and an

internal word counter. Its falling edge synchronizes the counters, and this can

occur at any submultiple of 8 kHz.

ADPCM_STB and PCM_STB are output timing signals that can be used to

enable three-state inputs to the parallel input bus and to clock the parallel output

bus signals. They are each low for two clock cycles. The rising edge of each

signal can be used to clock the parallel output data into an octal register.

2.1.2 Microprocessor Interface

An integral control interface to an Intel 8051-family microprocessor, Motorola

68HC11-family, or equivalent is provided. This microprocessor interface allows

the operation mode and the per-channel configuration of the Bt8110/8110B to be

selected directly from a software-based system. The use of this interface is

optional; it is enabled by setting the MICREN control input high. When MICREN

is set high, all mode and per-channel configuration is done through the

microprocessor. The microprocessor being used should be connected as shown in

Table 2-1.

The microprocessor interface to the Bt8110/8110B consists of 11 pins: µP

enable (MICREN) address latch enable (ALE), write enable (WR*), chip select

(CS), and seven multiplexed address/data bits (AD[6:0]). These signals are

connected as shown in Table 2-1.

The microprocessor interface is designed to allow the direct connection of an

Intel 8051-family or Motorola 68HC11 microprocessor. The chip select input can

be taken from one of the address inputs or from an address decoding circuit to

locate the Bt8110/8110B within any desired memory address range. The chip

select input to the Bt8110/8110B allows the control of multiple circuits from a

single microprocessor.

The microprocessor interface is write-only. Data read from the address space

of the Bt8110/8110B will be invalid.

100060C

Conexant

2-3

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