PEB 2091
PEF 2091
Functional Description
3.6
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.
3.6.1
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. For IOM®-2 mode setting refer to
"Setting Operating Modes", page 50.
The data is clocked by a Data Clock (DCL) that operates at twice the data rate.
Note 7:
This is the default setting. If the microprocessor mode and the master mode
are being used, DCL frequency can be set to the bit data rate, see "Setting
IOM®-2 Bit Clock Mode", page 56 for details. This section will deal with the
default setting. Nevertheless, it applies to the bit clock mode as well if DCL
frequencies are adjusted.
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 23
IOM®-2 Clocks and Data Lines
Note 8:
A device with an IOM®-2 interface is said to be in the ’IOM®-2 Master Mode’
or sometimes just ’Master Mode’ if the IOM®-2 clocks FSC and DCL are
delivered by this device. It is said to be in the ’IOM®-2 Slave Mode’ or
sometimes just ’Slave Mode’ if the IOM®-2 Clocks are input to this device.
Semiconductor Group
70
Data Sheet 01.99
INFINEON [ Infineon ]
