CSP1027 Datasheet, PDF (22/64 Pages) Agere Systems – CSP1027 Voice Band Codec for Cellular Handset and Modem Applications

CSP1027 Voice Band Codec for
Cellular Handset and Modem Applications
4 Architectural Information (continued)
VDD
SMODE0
SMODE1
SMODE2
CSP1027
Data Sheet
December 1999
DSP
D/A DATA
A/D DATA
CLOCK
CONTROL/DATA ADDRESS
INPUT/OUTPUT LOAD
Figure 23. Active Communication and Connections
5-7591 (F)
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.
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Lucent Technologies Inc.