XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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385
Setting this bit-field to "1" configures the Transmit DS3/E3 Framer block to automatically set the FEBE and
FERF bit-fields (within the outbound E3 data stream) to states based upon conditions detected by the Receive
DS3/E3 Framer block.
N
OTE
:
In this mode, the Transmit DS3/E3 Framer block will set and clear the FERF and FEBE bit-fields in response to the
following conditions.
A. FERF bit-field
If the Receive DS3/E3 Framer block (in the same channel) is currently experiencing an LOS, AIS or LOF
condition, then the Transmit DS3/E3 Framer block will automatically set the FERF bit-field (in the outbound E3
frame) to "1". Conversely, if the Receive DS3/E3 Framer block is not experiencing any of these conditions,
then the Transmit DS3/E3 Framer block will set the FERF bit-field (in the outbound E3 frame) to "0".
B. FEBE bit-field
If the Receive DS3/E3 Framer block detects a BIP-8 error in the incoming E3 frame, then the Transmit DS3/E3
Framer block will automatically set the FEBE bit-field (in the outbound E3 frame) to "1". Conversely, if the
Receive DS3/E3 Framer block does not detect a BIP-8 error in the incoming E3 frame, then the Transmit DS3/
E3 Framer block will set the FEBE bit-field (in the outbound E3 frame) to "0".
Setting this bit-field to "0" configures the Transmit DS3/E3 Framer block to set the FEBE and FERF bit-fields
(within the outbound E3 data stream) to the values residing within the FEBE and FERF bit-fields within the
TxE3 MA Byte Register (Address = 0x36), as illustrated below.
6.2.4.2.2
The XRT72L50 Framer IC contains 16 bytes worth of Transmit Trail Trace Buffer registers and 16 bytes worth of
Receive Trail Trace Buffer registers. The role of the Receive Trail Trace Buffer registers are described in
Section 6.1.1.3
.
The XRT72L50 Framer IC contains 16 Transmit Trail Trace Buffer registers (e.g., Tx TTB-0 through TxTTB-15).
The purpose of these registers are to provide a 16-byte Trail Access Point Identifier to the Remote Terminal
Equipment. The Remote Terminal Equipment will use this information in order to verify that it is still receiving
data from its intended transmitter. The specific use of these registers follows.
For Trail Trace Buffer Message purposes, the Transmit E3 Framer block will group 16 consecutive E3 frames,
into a Trail Trace Buffer super-frame. When the Transmit E3 Framer block is generating the first E3 frame,
within a Trail Trace Buffer super-frame, it will read in the contents of the Tx TTB-0 Register (Address = 0x38)
and insert this value into the TR byte-field of this very first Outbound E3 frame. When the Transmit E3 Framer
is generating the very next E3 frame (e.g., the second E3 frame, within the Trail Trace Buffer super-frame), it
will read in the contents of the Tx TTB-1 register (Address = 0x39) and insert this value into the TR byte-field of
this Outbound E3 frame. As the Transmit E3 Framer block is creating each subsequent E3 frame, within this
Trail Trace Buffer super frame, it will continue to increment to the very next Transmit Trail Trace Buffer register.
The Transmit E3 Framer block will then read in the contents of this particular Transmit Trail Trace Buffer register
(Tx TTB-n) and insert this value into the TR byte-field of the very next Outbound E3 frame. After the Transmit
E3 Framer block has created the 16th E3 frame, within a given Trail Trace Buffer super-frame (e.g., it has read
in the contents of Tx TTB-15 register and has inserted this value into the TR byte of the 16th E3 frame), it will
begin to create a new Trail Trace Buffer super-frame, by reading the contents of the Tx TTB-0 register, and
repeating the above-mentioned procedure.
The contents of the Tx TTB-0 register will typically be of the form [1, C6, C5, C4, C3, C2, C1, C0]. The “1” in
the MSB (Most Significant bit) position of this byte is used to designate that this octet is the frame-start marker
(e.g., is the first of the 16 TR bytes, within a Trail Trace Buffer super-frame). The remaining Trail Trace Buffer
registers (TxTTB-1 through TxTTB-15) will typically contain a “0” in their MSB positions. The remaining bits
Configuring the Transmit Trail Trace Buffer Message
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
FERF
FEBE
PLDType
Payload Dependent
Timing Marker
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
X
X
0
1
0
0
0
0