IBM3009K2672
IBM SONET/SDH Framer
parent mode is selected, the SONET/SDH framer will take the TXUDATA(15:0) data and insert each entire
chunk into the transmit SONET/SDH frame without modification or the data can be optionally scrambled. The
TXSOFI, TXEOFI and TXMSI pins are not used when the SONET/SDH framer is in transparent mode and
should be tied low. If the SONET/SDH framer is set to not perform any FCS processing it will just take the
TXUDATA(15:0) chunk data and insert frame delimiting flags around the frames and stuff the control escape
and flag characters between the frame delimiting flags per [RFC1662]. As in the other cases, the data can
optionally be scrambled. When FCS processing is disabled, it is expected that the TXUDATA(15:0) will con-
tain the appropriate FCS.
Transmit UTOPIA Level 2+ Interface Operation for Non-Transparent Mode (16-Byte Chunks)
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
TXUCLK1
(Input)
TXUADDR(4:0)
(Inputs)
N
M
M
Chunk 1 of PHY N
Chunk 2 of PHY N
Chunk 1 of PHY M
TXUDATA(15:8)
(Inputs)
TXUDATA(7:0)
(Input)
TXENB
(Input)
TXSOC
(Input)
TXSOFI
(Input)
TXEOFI
(Input)
TXMSI
(Input)
= Fill
The previous figure shows the transfer of frames across the transmit UTOPIA Level 2+ interface. The
TXABTO, TXCLAV(0), and TXPRTY signals are omitted to avoid clutter. The polling and selection of PHYs is
identical to that in the ATM mode operation, which is also described in [UL2v1]. The TXUADDR(4:0), TXENB,
TXCLAV(0), TXSOC and TXPRTY signals therefore behave the same as their ATM counterparts, with the
exception that TXCLAV(0) indicates that the SONET/SDH framer can accept at least a complete chunk of
data. As stated earlier, a chunk is analogous to a cell. Chunk size is programmable to be either 16, 32, 48, or
64 bytes. Transmit UTOPIA Level 2+ Interface Operation for Non-Transparent Mode (16-Byte Chunks) on
page 16 shows the transfer of a 27-byte block of frame data using two back-to-back chunks over PHY N, a 6-
byte block of frame data over PHY M, and the start of another block of frame data also over PHY M. The
chunk size shown is 16 bytes. PHY N is selected on clock edge 1. TXENB is used to indicate valid data and
control signals at the interface. On clock edge 2, TXSOC is sampled as a ’1’, thus indicating the start of a
chunk. Also, on clock edge 2, TXSOFI is sampled high, which indicates the start of a new block of frame data.
The block of frame data for PHY N is transferred from clock edge 2 to clock edge 15. The end of this block of
frame data is indicated by the TXEOFI signal asserted high. The TXMSI signal is asserted with the TXEOFI
signal to indicate that the last byte of the frame is in the Most Significant Byte (MSB) position of that word.
The Least Significant Byte (LSB) of that word contains fill. Since there is no more frame data to transfer
across PHY N, 2 fill words are added to round out Chunk 2 of PHY N. Fill is data that is used to fill up empty
locations in the data stream not occupied by frame data. This fill is either discarded or converted into inter-
frame flags (7E H) by the SONET/SDH framer. Another block of frame data is transferred across PHY M on
Block Diagram and Block Descriptions
Page 16 of 279
ssframer.01
8/27/99
IBM [ IBM ]
