Preliminary Information
Pin Description (Continued)
Pin #
16
Name
ADI
Description
MH89790B
Alternate Digit Inversion (Input):
If this input is high, the CEPT timeslots which are
specified on CSTi0 as voice channels are ADI coded and decoded. When this bit is low
it disables ADI coding for all channels. This feature allows either ADI or non-ADI codecs
to be used on DSTi and DSTo. Internally pulled with a 4.7kΩ resistor to +V
DD
.
Data ST-BUS Input:
This pin accepts a 2048 kbit/s serial stream which contains the 30
PCM or data channels to be transmitted on the CEPT trunk.
2048 kbit/s System Clock (Input):
The master clock for the ST-BUS section of the
chip. All data on the ST-BUS is clocked in on the falling edge of the C2i and output on the
rising edge. The falling edge of C2i is also used to clock out data on the CEPT PCM 30
transmit link.
2048 kHz Extracted Clock (Output):
Internally connected to pin 3.
Frame Pulse Input:
The ST-BUS frame synchronization signal which defines the
beginning of the 32 channel frame.
Ground.
D.C. Power Return.
PAD Input:
Input to the symmetrical resistive 75 ohm T-type line matching circuit. In a
typical application connect this input to the output of the line driving transformer.
Transmit Ground:
Common point of the T-type PAD circuit. Connect to GND in a typical
application.
PAD Output:
Output from the T-type PAD circuit. Output impedance of the PAD is pure
resistive 75Ω.
Output A (Open Collector Output):
This is the output of the CEPT transmitter. It is
suitable for use with an external pulse transformer to generate the transmit bipolar line
signal.
Transmit Multiframe Boundary (Input):
This input can be used to set the channel
associated and CRC transmitted multiframe boundary (clear the frame counters). If a
transmit multiframe signal is not being generated externally to the device, the MH89790B
will internally generate its own multiframe when this pin is tied high.
Received Multiframe Boundary (Output):
An output pulse delimiting the received
multiframe boundary. (This multiframe is not related to the received CRC multiframe.)
No Connection.
Output B (Open Collector Output):
Output of the CEPT transmitter. It is suitable for
use with an external pulse transformer to generate the transmit bipolar line signal.
No Connection.
Data ST-BUS Output:
A 2048 kbit/s serial output stream which contains the 30 PCM or
data channels received from the CEPT line.
No Connection.
Ground.
D.C. Power Return.
No Connection.
Loss of Signal (Output):
This pin goes High when 128 contiguous ZEROs are received
on the RxT and RxR inputs. When LOS is High, RxA and RxB are forced High. LOS is
reset when 64 ONEs are received in a two E1-frame period.
No Connection.
17
18
DSTi
C2i
19
20
21
22
23
24
25
E2o
F0i
V
SS
PADi
TxG
PADo
OUTA
26
TxMF
27
28
29
30
31
32
33
34 - 37
38
RxMF
NC
OUTB
NC
DSTo
NC
V
SS
NC
LOS
39 - 40
NC
4-189
MITEL [ MITEL NETWORKS CORPORATION ]
