IBM3009K2672
IBM SONET/SDH Framer
Note: When FCSABT is set to ‘0’, the RXABTO pin indicates detection of one of the abort conditions listed
previously. In MPHY mode, if an abort condition is detected in a PHY, say PHY N, while PHY M is being
accessed, the RXABTO indication for PHY N will not be output until PHY N is selected. When an abort condi-
tion occurs, the rest of the received frame is ignored and used to fill up the chunk until the end of the chunk is
reached or until a new frame is received. When FCSABT is set to ‘1’, the RXABTO pin is forced low and the
RXFCSEO pin is used to indicate both FCS errors and aborts. The abort signalling described above is the
same except that the abort is signalled on the RXFCSEO pin.
Another block of frame data is transferred across PHY M on clock edges 21-23. The RXMSO signal is
asserted with the RXEOFO coincident with clock edge 23 to indicate that the last byte of the block of frame
data is in the LSB of that word. A word of fill is present in clock edge 24. There can be any number of fill
words between frames in a chunk. Since the SONET/SDH framer only transfers complete chunks, fill is
added to a chunk after the end of a frame to fill out the chunk in lieu of frame data as shown in Receive UTO-
PIA Level 2+ Interface Operation for Non-Transparent Mode (16-Byte Chunks) on page 18. That is, after the
end of a frame, fill is inserted into the chunk until either new frame data is received or until the end of the
chunk occurs. A chunk will never start with fill. If a block of frame data ended in a chunk that was being trans-
ferred across PHY X, and that chunk ended before another block of frame data started, then the start of the
next block of frame data across PHY X will start in the first word of the next chunk transferred across PHY X.
If an abort occurs, the rest of the aborted frame data will be used as fill. This fill will only be used to fill the cur-
rent chunk until a new frame is received. If the end of the chunk occurs before a new frame is received, the
rest of the data will be discarded and the next chunk transferred across that PHY will contain the next
received frame. A frame always starts on the MSB of a word.
Telecom Bus Interface
The SONET/SDH framer contains four full duplex Telecom Bus interfaces, numbered 1 through 4, one Tele-
com Bus for each STM-1/STS-3c in 4 x STM-1/STS-3c mode, or one Telecom Bus for each AU-4 that may be
contained in an STM-4/STS-12 signal. When STM-4c or STS-12c payloads are processed, the four Telecom
Bus interfaces act in unison as a 32-bit wide Telecom interface.
Note: POH processing is not performed when the SONET/SDH framer is operating in Telecom Bus mode. All
POH in the transmit direction are derived from what is input at the transmit Telecom Bus inputs. All POH at the
receive Telecom Bus interface are derived directly from the line.
In the transmit direction, the Telecom Bus interface supports either the AU-4 or VC-4 formats on a per Tele-
com Bus basis. When the AU-4 format is selected, the device driving the transmit Telecom Bus must supply
the H1 and H2 pointer bytes. The SONET/SDH framer will use all of the H1 and H2 pointer bytes supplied to
it and pass them on to the transmit line. It should be noted that there are 6 bytes (3 H1 and 3 H2) that must be
supplied. When the VC-4 format is selected, the SONET/SDH framer performs pointer retiming where it cal-
culates and inserts a pointer value into the outgoing SDH Frame. In the receive direction, the entire received
payload is passed, unmodified, to the receive Telecom Bus. Therefore, in 4 x STM-1/STS-3c mode, each
STM-1/STS-3c frame is passed to its corresponding Telecom Bus interface. In STM-4/STS-12 mode, all of the
data from column 1 in the received frame is passed to receive Telecom Bus #1, all of the data from column 2
in the received frame is passed to receive Telecom Bus #2, etc. In STM-4c/STS-12c mode the same principle
of operation applies as in the case of the STM-4/STS-12 mode, except that the RXTB#SPE, C1J1, and FAIL
outputs have identical signals on them, where # = 1, 2, 3, 4.
The SONET/SDH framer’s Telecom Bus interface supports the following features:
• Option to enable/disable parity checking.
• Option to select if parity is calculated/checked over data only or data and SPE and C1J1 and FAIL sig-
nals.
ssframer.01
8/27/99
Block Diagram and Block Descriptions
Page 19 of 279
IBM [ IBM ]
