CX28344 Conexant, CX28344 Datasheet - Page 74

• Manufacturer Part Number: CX28344
• Description: (CX2834x) Dual / Triple / Quad / Hex / Octal - Enhanced DS3 / E3 Framer
• Manufacturer: Conexant

Functional Description
2-28
FLAG Transmission
The TDL machine generates and transmits flag sequence (01111110) automatically in
the following cases:
Abort Message Transmission
Abort is defined in ISO-3309 as a sequence of seven or more continuous 1s.
The abort message that is generated by the transmit circuitry is a sequence of 16
continuous 1s. It is generated automatically as a result of an underrun condition.
When underrun occurs, the transmit generates only one abort sequence followed by at
least two FLAG sequences before transmitting the next message.
For the system to intentionally send an ABORT sequence during a message
transmission without damaging other messages stored in the TDL FIFO buffer, the
system should stop writing new data bytes to the FIFO buffer. In addition, the system
should not write an EOM data byte, and wait until the FIFO buffer is emptied. When
the FIFO buffer is emptied, an underrun occurs which results in sending the desired
Abort sequence.
1.
2.
3.
4.
After enabling the data link, FLAG sequences are transmitted automatically until
a new message starts. At least two FLAG sequences are transmitted before the
new message begins.
Between two consecutive transmitted messages, two FLAG sequences are
automatically inserted. In case the FIFO buffer contains more than one message
(after FCS sequence is transmitted, if FCS transmission is enabled), the
transmitter sends two FLAG sequences after the last byte of the previous message
is sent before starting transmission of the first byte of the new message (the next
byte to be transmitted at the FIFO buffer after an EOM byte).
If the current message is the last message in the FIFO buffer (FIFO is empty, and
the last byte is indicated as an end of message byte), the transmitter sends FLAG
sequences continuously after the end of the message and as long as the FIFO
buffer is empty.
After sending one abort sequence (sixteen 1s in underrun condition) the
transmitter automatically starts transmitting FLAG sequences for as long as the
FIFO buffer is empty (at least two FLAG sequences are transmitted before
starting a new message).
Mindspeed Technologies™
CX28342/3/4/6/8 Data Sheet
28348-DSH-001-B