PSB21911 데이터 시트보기 (PDF) - Infineon Technologies

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PSB21911

ICs for Communications ISDN Echocancellation Circuit for Terminal Applications IEC-Q TE

Infineon Technologies 

PSB 21911

PSF 21911

IOM®-2 Interface

2.3

IOM®-2 Interface

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

IOM®-2 Frame Structure

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®-2 Clocks and Data Lines

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

Semiconductor Group

30

11.97

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