PEB2055 datasheet(39/269 Pages) INFINEON

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PEB 2055

PEF 2055

Operational Description

Semiconductor Group

Time slot switching is always carried out on 8-bit time slots, the actual position and

number of transferred bits can however be limited to 4-bit or 2-bit sub time slots within

these 8-bit time slots. On the CFI side, only one sub time slot per 8-bit time slot can be

switched, whereas on the PCM-interface up to 4 independent sub time slots can be

switched.

Examples are given in chapter 5.3.

Sub Time Slot Switching

Sub time slot positions at the PCM-interface can be selected at random, i.e. each single

PCM time slot may contain any mixture of 2- and 4-bit sub time slots. A PCM time slot

may also contain more than one sub time slot. On the CFI however, two restrictions must

be observed:

– Each CFI time slot may contain one and only one sub time slot.

– The sub-slot position for a given bandwidth within the time slot is fixed on a per port

basis.

For more detailed information on sub-channel switching please refer to chapter 5.4.2.

µP Transfer

Switching paths 3 and 4 of figure 18 can be realized for all available time slots. Path 3

can be implemented by defining the corresponding CFI time slots as “

µP channels” or as

“pre-processed channels”.

Each single time slot can individually be declared as “

µP channel”. If this is the case, the

µP can write a static 8-bit value to a downstream time slot which is then transmitted

repeatedly in each frame until a new value is loaded. In upstream direction, the

µP can

read the received 8-bit value whenever required, no interrupts being generated.

The “pre-processed channel” option must always be applied to two consecutive time

slots. The first of these time slots must have an even time slot number. If two time slots

are declared as “pre-processed channels”, the first one can be accessed by the

monitor/feature control handler, which gives access to the frame via a 16-byte FIFO.

Although this function is mainly intended for IOM- or SLD-applications, it could also be

used to transmit or receive a “burst” of data to or from a 64-kbit/s channel. The second

pre-processed time slot, the odd one, is also accessed by the

µP. In downstream

direction a 4-, 6- or 8-bit static value can be transmitted. In upstream direction the

received 8-bit value can be read. Additionally, a change detection mechanism will

generate an interrupt upon a change in any of the selected 4, 6 or 8 bits.

Pre-processed channels are usually programmed after Control Memory (CM) reset

during device initialization. Resetting the CM sets all CFI time slots to unassigned

channels (CM code “0000”). Of course, pre-processed channels can also be initialized

or re-initialized in the operational phase of the device.

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