CSP1027 datasheet(22/64 Pages) AGERE

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CSP1027 Voice Band Codec for

Data Sheet

Cellular Handset and Modem Applications

December 1999

Lucent Technologies Inc.

4 Architectural Information (continued)

Figure 23. Active Communication and Connections

4.6.5 Active I/O Configuration (SMODE[1:0] = 01)

The active SIO configuration causes the CSP1027 to

generate an active input/output load (SYNC) to perform

input/output transmissions when needed. The user

supplies only a serial input/output clock (IOCK).

The active SIO is selected by setting SMODE1 low and

SMODE0 high. The input/output clock (IOCK) is an

input and the input/output load (SYNC) is an output.

While the codec is inactive, ACTIVE = 0 (see Table 7

on page 26), SYNC generates serial I/O transfers at an

IOCK ÷ 16 rate to allow loading the codec control regis-

ters, cioc[0:3]. While the codec is active, ACTIVE = 1

(see Table 7 on page 26), SYNC generates serial I/O

transfers at the sampling rate, synchronized to the

codec's emptying of the cdx(D/A) and loading of the

cdx(A/D). The serial address (SADD) functions as

described previously for the passive SIO configuration,

but with the SYNC pin being active and determining

data transfers, the need for polling the codec STATUS

flag is eliminated. The serial address during the data

stream still is used to determine whether data in the

input shift register is latched into cdx(D/A) or cioc[0:3]

at the end of the transaction. Note that cioc0, with

ACTIVE = 1, should be written last since this will

change the rate of serial I/O transfers from IOCK ÷ 16

to the sampling rate.

An example of the active SIO configuration is shown in

Figure 23. The DSP supplies the serial clock (IOCK)

while the CSP1027 supplies the input/output load,

SYNC. The serial address (SADD) is connected so that

writing the DSP's srta register addresses the cdx(D/A)

when srta = 0x0, or the cioc0, cioc1, cioc2, cioc3

when srta = 0x1. The DSP can activate the codec by

writing the cioc0 register in the CSP1027, and then let-

ting its input buffer full flag (IBF) indicate when the

CSP1027 has transferred data. This is the preferred

interface for a single DSP and a CSP1027.

A/D DATA

CLOCK

CONTROL/DATA ADDRESS

INPUT/OUTPUT LOAD

DSP

CSP1027

SMODE0

SMODE1

SMODE2

D/A DATA

VDD

5-7591 (F)

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