psf21911 ETC-unknow, psf21911 Datasheet - Page 30

• Manufacturer Part Number: psf21911
• Description: Isdn Echocancellation Circuit Terminal Applications Iec-q
• Manufacturer: ETC-unknow

Semiconductor Group
2.3
The IOM-2 interface is used to interconnect telecommunication ICs. It provides a
symmetrical full-duplex communication link, containing user data, control/programming
and status channels. The structure used follows the 2B + 1D-channel structure of ISDN.
The ISDN user data rate of 144 kbit/s (B1 + B2 + D) is transmitted in both directions over
the interface.
The IOM-2 interface is a generalization and enhancement of the IOM-1 interface.
2.3.1
The IOM-2 interface comprises two clock lines for synchronization and two data lines.
Data is carried over Data Upstream (DU) and Data Downstream (DD) signals. The
downstream and upstream direction are always defined with respect to the exchange.
Downstream refers to information flow from the exchange to the subscriber and
upstream vice versa respectively. The IOM-2 Interface Specification describes open
drain data lines with external pull-up resistors. However, if operation is logically point-to-
point, tristate operation is possible as well.
The data is clocked by a Data Clock (DCL) that operates at twice the data rate. Frames
are delimited by an 8-kHz Frame Synchronization Clock (FSC). Incoming data is
sampled on every second falling edge of the DCL clock.
Figure 11 IOM
Within one FSC period 32 bit or 96 bit are transmitted, corresponding to DCL
frequencies of 512 kHz or 1.536 MHz.
Two optimized IOM-2 timing modes exist:
– NT mode for NT1 applications
– TE mode for terminal and intelligent NT applications
IOM
IOM
®
®
®
-2 Clocks and Data Lines
-2 Interface
-2 Frame Structure
30
IOM®-2 Interface
PSB 21911
PSF 21911
11.97