![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT94L33IB-L_datasheet_100163/XRT94L33IB-L_303.png)
xr
XRT94L33
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
Rev.1.2.0.
303
STEP 2 – Write the value “0” into Bit 7 (M0M1 Insert Method[0]) within the “Transmit STS-3 Transport
– SONET Transmit Control Register – Byte 0”; as depicted below.
Transmit STS-3 Transport – SONET Transmit Control Register – Byte 0 (Address = 0x1902)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
M0M1 Insert
Method[0]
Unused
RDI-L Force
AIS-L Force
LOS Force
Scramble
Enable
B2 Error
Insert
A1A2 Error
Insert
R/W
R/O
R/W
0
Steps 1 and 2 configure the Transmit STS-3 TOH Processor block to automatically set bits 5 through 8 (of the
M0 Byte) within the “outbound” STS-3 data-stream, to the appropriate REI-L value based upon receive
conditions as detected by the corresponding “Receive STS-3 TOH Processor” block.
STEP 3 – Indicate whether or not the REI-L value (transmitted to the remote LTE) reflects the number
of bits (within the B2 byte) that are in error, or the number of erred STS-3 frames that have been
detected by the corresponding Receive STS-3 TOH Processor block.
The XRT94L33 permits the user to (1) flag B2 byte errors, and (2) to transmit the resulting REI-L values (back
to the remote LTE) by the following means.
By flagging and reporting the number of bits (within the B2 byte(s)) that have been determined to be in
error, within a given STS-3 frame.
By flagging and reporting whether or not the corresponding Receive STS-3 TOH Processor block is
currently receiving an erred STS-3 frame.
The user can choose between these two options by writing the appropriate value into Bit 1 (B2 Error Type)
within the “Receive STS-3 Transport – Control Register – Byte 0”, as depicted below.
Receive STS-3 Transport Control Register – Byte 0 (Address = 0x1103)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
SF Detect
Enable
SD Detect
Enable
Descramble
Disable
SDH/SONET*
REI-L Error
Type
B2 Error
Type
B1 Error
Type
R/O
R/W
0
X
0
Setting this bit-field to “0” configures the “Transmit STS-3 TOH Processor” block to set the REI-L bit-fields
(within the M0 byte) of the “outbound” STS-3 frame to a value that reflects the number of bits (within the B2
byte) that were determined to be in error (within the most recently received STS-3 frame) by the
corresponding Receive STS-3 TOH Processor block. In this case, the REI-L bit-fields can range in value from
“0” (for no B2 byte errors) to “8” (for all B2 bits being in error).
Setting this bit-field to “1” configures the “Transmit STS-3 TOH Processor” block to set the REI-L bit-fields
(within the M0 byte) of the “outbound” STS-3 frame; to a value that indicates whether or not at least one B2 bit
error was detected within the most recently received STS-3 frame; by the corresponding Receive STS-3 TOH
Processor block. In this mode, the Transmit STS-3 TOH Processor block will set the “REI-L” bit-fields (within
the “outbound” STS-3 frame) to “0” if the corresponding Receive STS-3 TOH Processor block is not detecting
any B2 byte errors, in its incoming STS-3 data-stream.
Conversely, the Transmit STS-3 TOH Processor block will set the “REI-L” bit-fields (within the “outbound”
STS-3 frame) to “1” if the corresponding Receive STS-3 TOH Processor block receives an STS-3 frame that
contains a B2 byte error.