MT9125
configuration the ENB1 and ENB2 inputs are
ignored. If F0i is tied continuously to V
SS
, then SSI
operation will be assumed and the transcoder will
use the strobes connected to ENB1 and ENB2 as its
internal reference.
Power-Down Operation (PWRDN)
To minimize power consumption a pin selected,
power-down option is provided. Device power down
is accomplished by forcing the PWRDN pin to V
SS
.
This asynchronous control forces all internal clocking
to halt and the C2o, EN1, EN2, DSTo and ADPCMo
outputs to become tri-stated. Upon returning
PWRDN to V
DD
coincident with the next alignment
signal, all outputs will return to their active state and
the internal clocks are re-started. In this mode the
ADPCM algorithm is not reset to the 'optional reset
values', however, the self-convergent nature of the
algorithm will ensure that convergence of the
(AD)PCM streams will occur within 3496 frames as
specified by CCITT G.721.
Preliminary Information
Removal of the BCLK and MCLK inputs is not
necessary during power-down mode. If the device is
released from power-down without a valid MCLK the
ADPCMo and PCMo outputs will become active,
driving either continuous logic high or logic low, until
a MCLK signal is applied to resume internal
operation.
PWRDN is a schmidt trigger input.
Applications
Various configurations of Pair Gain drops are
depicted in Figures 7, 8 and 9. These show
applications using mixed ST-BUS/SSI, all ST-BUS
and all SSI implementations. Figure10 shows an ST-
BUS line card application for Pair Gain while Figure
11 shows a 2-channel, wireless-set, base station
application based upon ST-BUS.
V
DD
MT9125
BCLK
ENS
D
X
D
R
FS
X
FS
R
BCLK
X
MCLK
X
V
FRO
V
FxL+
V
FxL-
S
L
I
C
T
R
L
in
+
L
in
-
L
out
+
L
out
-
F0i
BCLK
MCLK
TX
RX
EN1
EN2
MCLK
ADPCMi
ADPCMo
ENA
DSTi
DSTo
ENB1
ENB2
T
R
D
X
D
R
FS
X
FS
R
BCLK
X
MCLK
X
V
FRO
V
FxL+
V
FxL-
S
L
I
C
T
R
Gate
Array
MT9125
BCLK
F0i
MCLK
ENS
V
DD
D
X
D
R
FS
X
FS
R
BCLK
X
MCLK
X
V
FRO
V
FxL+
V
FxL-
S
L
I
C
T
R
Ring
Generator
ADPCMi
ADPCMo
ENA
DSTi
DSTo
ENB1
ENB2
D
X
D
R
FS
X
FS
R
BCLK
X
MCLK
X
V
FRO
V
FxL+
V
FxL-
S
L
I
C
to SLICs
Hookswitch
from SLICs
T
R
Figure 9 - Pair Gain Application (SSI/SSI)
8-26
MITEL [ MITEL NETWORKS CORPORATION ]
