IBM3009K2672
IBM SONET/SDH Framer
• Option to select if odd or even parity is used.
• An 8-kHz transmit frame pulse and complementary transmit reference clock outputs are provided to syn-
chronize transmit data into the SONET/SDH framer. These pulses are also available when the UTOPIA or
UTOPIA Level 2+ interfaces are used.
• Retiming option can be activated on any transmit Telecom Bus (1-4) on a per Telecom Bus basis.
• Supports connections to mapper devices for TDM applications.
Transmit Telecom Bus
There are four transmit Telecom Bus interfaces, numbered 1 - 4, allowing the back-to-back connection of
SONET/SDH framers (if retiming is turned on), or connections to mapper devices.
Each transmit Telecom Bus interface of the SONET/SDH framer consists of the following inputs: 8-bit data
bus (TXTB#DATA(7:0)), clock (TXTB#CLK), SPE indication (TXTB#SPE), C1J1 indication (TXTB#C1J1),
parity (TXTB#PAR), and a failure indication (TXTB#FAIL). The SONET/SDH framer also provides a common
set of reference timebase signals for synchronizing the data input to each of the Telecom Bus ports for the
cases where transmit retiming is not enabled. This reference timebase interface consists of the following out-
puts: a Transmit Reference Clock and its complement (TXCCLK and TXCCLK) and a Transmit Reference
Frame Pulse (TXCFRM).
All of the Telecom Bus ports operate at 19.44 MHz. Furthermore, the option to support either a VC-4 (Trans-
mit Retiming On) or AU-4 (Transmit Retiming Off) format is provided via the GContTx#(1:0) (#=1-4) control
bits in the GContTx register. Retiming of the transmit Telecom Bus signal is performed when the VC-4 signal
format is selected. Retiming is the process of calculating the pointer value based on the phase difference of
the input VC-4 and the output frame. That is, pointer adjustments are allowed to occur to compensate for the
phase changes between the input VC-4 signal and the phase of the transmit SONET/SDH frame that may
occur due to clock offsets.
Transmit retiming is enabled on a per Telecom Bus basis by setting the corresponding GContTx#(1:0) bits to
VC-4 mode. When transmit retiming is enabled on a particular Telecom Bus, its transmit signals (clock, data,
SPE, etc.) only need to be synchronous to its TXTB#CLK and not to the TXCCLK signal. The J1 and C1
pulses in the TXTB#C1J1 signal are mandatory for the Telecom Bus channels where transmit retiming is
enabled. The SONET/SDH framer will calculate a pointer and insert it into the outgoing SDH stream. The
SONET/SDH framer will cause pointer adjustments to occur to compensate for the difference in the frequen-
cies between the TXTB#CLK and TXCCLK clocks. Furthermore, the SONET/SDH framer can accept pointer
adjustments on its transmit Telecom Bus input and still perform retiming in an error-free fashion.
When transmit retiming is disabled, the transmit Telecom Bus device that is providing data to the
SONET/SDH framer must supply an AU-4, that is a VC-4 with valid payload pointer bytes including concate-
nation indication bytes as applicable.
When the SONET/SDH framer is processing an STM-4c/STS-12c signal, all four Telecom Bus ports operate
in parallel as one 32-bit wide Telecom Bus. All input signals must be driven (i.e., all clock, all SPE, all C1J1,
etc.). In this case the transmit Telecom Bus data needs to be double word aligned. The receive Telecom Bus
data is provided double word aligned.
The Telecom Bus interface signals, TXCCLK and TXCCLK, are provided as a reference clock for devices to
put data out onto the Telecom Bus ports of the SONET/SDH framer. These signals have a frequency of
19.44 MHz. If transmit retiming is not selected via the GContTx#(1:0) control bits, one of these clocks must be
used to source the data to be transmitted on the appropriate Telecom Bus.
An 8-kHz pulse (TXCFRM) is output on the falling edge of TXCCLK once every frame period and is one TXC-
Block Diagram and Block Descriptions
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ssframer.01
8/27/99
IBM [ IBM ]
