DS26401 Datasheet, PDF (144/309 Pages) Dallas Semiconductor – Octal T1/E1/J1 Framer

DS26401 Octal T1/E1/J1 Framer
9.20 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 4.096 MHz bus speed allows two PCM data
streams to share a common bus. The 8.192 MHz bus speed allows four PCM data streams to share a common
bus. The 16.384 MHz 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
TIBOC register.
9.20.1 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-low signal (TIBO_OEB) during bus active times. TIBO_OEB can be
used for bus multiplexer or tri-state buffer control.
9.20.2 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.
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