DS26401 datasheet(208/309 Pages) DALLAS

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DS26401 Octal T1/E1/J1 Framer

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10.17 Interleaved PCM Bus Operation (IBO)

In many architectures, the PCM outputs of individual framers are combined into higher speed PCM buses to

simplify transport across the system backplane. The DS26401 can be configured to allow PCM data to be

multiplexed into higher speed buses eliminating external hardware, saving board space and cost. The DS26401 can

be configured for channel or frame interleave.

The interleaved PCM bus option (IBO) supports three bus speeds. The 4.096MHz bus speed allows two PCM data

streams to share a common bus. The 8.192MHz bus speed allows four PCM data streams to share a common bus.

The 16.384MHz bus speed allows 8 PCM data streams to share a common bus. The receive elastic stores of each

transceiver must be enabled. Via the IBO register the user can configure each framer for a specific bus position.

For all IBO bus configurations each framer is assigned an exclusive position in the high speed PCM bus. The 8kHz

frame sync can be generated from the system backplane or from the first device on the bus. All other devices on

the bus must have their frame syncs configured as inputs. Relative to this common frame sync, the devices will

await their turn to drive or sample the bus according to the settings of the DA0, DA1 and DA2 bits of the RIBOC

10.17.1 Channel Interleave

In channel interleave mode data is output to the PCM Data Out bus one channel at a time from each of the

connected DS26401s until all channels of frame n from each framer has been placed on the bus. This mode can be

used even when the DS26401s are operating asynchronous to each other. The elastic stores will manage slip

conditions. The DS26401 provides an active high signal (RIBO_OE) during bus active times. RIBO_OE can be used

for bus multiplexer or tri-state buffer control.

10.17.2 Frame Interleave

In frame interleave mode data is output to the PCM Data Out bus one frame at a time from each of the framers.

This mode is used only when all connected DS26401s are operating in a synchronous fashion (all inbound T1 or E1

lines are synchronous) and are synchronous with the system clock (system clock derived from T1 or E1 line). In this

mode, slip conditions are not allowed.

DS26401 Datasheet(PDF) 208 Page - Dallas Semiconductor