STANDARD PRODUCT
PM5365 TEMAP
DATASHEET
PMC-1991148
ISSUE 3
HIGH DENSITY VT/TU MAPPER
AND M13 MULTIPLEXER
C: Stuff Control bit - set to logic ‘1’ for stuff indication
S: Stuff Opportunity bit - when stuff control bit is ‘0’, stuff opportunity is I bit
O: Overhead
I: E1 payload information
The RTDM buffers the tributary synchronous payload envelope bytes of the
incoming tributaries in individual FIFOs to accommodate tributary pointer
justifications.
The RTDM performs majority voting on the tributary stuff control (C1, C2) bits. If
the majority of each set of the stuff control bits indicate a stuff operation, then the
associated stuff opportunity bit (S1, S2) will not carry T1 or E1 payload.
Conversely, if the majority of the stuff control bits indicate a data operation, the
appropriate stuff opportunity bit(s) will carry T1 or E1 payload. At each
multiframe boundary, the RTDM indicates to the down stream parallel to serial
converter (PISO) the status of the stuff control bits. For T1 streams, the parallel
to serial converter can be controlled to generate 771, 772 or 773 T1 clock cycles.
For E1 streams, the number of clock cycles is controllable to 1023, 1024 or
1025.
The RTDM attenuates jitter introduced by pointer justification events. Tributary
payload data is held in a FIFO. When a pointer justification is detected, the
RTDM issues evenly spaced commands to the down stream parallel to serial
converter block which makes 1/12 UI adjustments to the phase of its generated
T1 output clock or 1/9 UI adjustments to the E1 clock. The number of
commands sent per incoming pointer justification is based on the observation
that four T1 or E1 frames are delivered or deleted for each full round of 104
VT1.5 (TU-11) or 140 VT2 (TU-12) pointer justifications.
9.18 Parallel In to Serial Out Converter (PISO)
The Parallel In to Serial Out Converter (PISO) serializes up to 28 T1 or 21 E1
tributaries which have been demapped from the STS-1 SPE or STM-1AU3 or
VC3 via the Receive Tributary Demapper (RTDM). In conjunction with the
Receive Tributary Demapper (RTDM) this block performs the desynchronizer
function to provide a low jitter T1 or E1 serial clock and data.
The Desynchronizer uses a combination of two clock generation techniques to
desynchronize the demapped T1s and E1s. Incoming bit stuff events cause an
extra bit of data to be generated or removed from the generated serial stream
over the following 2KHz multi-frame. Pointer justifications are spread out by
advancing or retarding the generated T1 or E1 clock phase.
Proprietary and Confidential to PMC-Sierra, Inc. and for its Customers’ Internal Use
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PMC [ PMC-SIERRA, INC ]
