tfra08c13 ETC-unknow, tfra08c13 Datasheet - Page 91

• Manufacturer Part Number: tfra08c13
• Description: Tfra08c13 Octal T1/e1 Framer
• Manufacturer: ETC-unknow

Preliminary Data Sheet
October 2000
Lucent Technologies Inc.
Lucent Technologies Inc.
Facility Data Link
Transmit ANSI Performance Report Messages (PRM)
When the ANSI PRM mode is enabled by setting register FDL_PR1 bit 7 to 1, the transmit FDL assembles and
transmits the ANSI performance report message once every second.
After assembling the ANSI PRM message, the receive framer stores the current second of the message in regis-
ters FRM_SR62 and FRM_SR63 and transfers the data to the FDL transmit FIFO. After accumulating three sec-
onds (8 bytes) of the message, the FDL transmit block appends the header and the trailer (including the opening
and closing flags) to the PRM messages and transmits it to the framer for transmission to the line.
Table 39—Table 41 show the complete format of the PRM HDLC packet.
HDLC Operation
HDLC operation is the default mode of operation. The transmitter accepts parallel data from the transmit FIFO, con-
verts it to a serial bit stream, provides bit stuffing as necessary, adds the CRC-16 and the opening and closing
flags, and sends the framed serial bit stream to the transmit framer. HDLC frames on the serial link have the follow-
ing format.
Table 43. HDLC Frame Format
All bits between the opening flag and the CRC are considered user data bits. User data bits such as the address,
control, and information fields for LAPB or LAPD frames are fetched from the transmit FIFO for transmission. The
16 bits preceding the closing flag are the frame check sequence, cyclic redundancy check (CRC), bits.
Zero-Bit Insertion/Deletion (Bit Stuffing/Destuffing)
The HDLC protocol recognizes three special bit patterns: lags, aborts, and idles. These patterns have the common
characteristic of containing at least six consecutive ones. A user data byte can contain one of these special pat-
terns. Transmitter zero-bit stuffing is done on user data and CRC fields of the frame to avoid transmitting one of
these special patterns. Whenever five ones occur between flags, a 0 bit is automatically inserted after the fifth 1,
prior to transmission of the next bit. On the receive side, if five successive ones are detected followed by a 0, the 0
is assumed to have been inserted and is deleted (bit destuffing).
Opening Flag
01111110
User Data Field
(continued)
8 bits
Sequence (CRC)
Frame Check
16 bits
TFRA08C13 OCTAL T1/E1 Framer
Closing Flag
01111110
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