XRT72L56 Datasheet, PDF (408/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
áç
PRELIMINARY
FIGURE 175. FLOW CHART DEPICTING HOW TO USE THE LAPD TRANSMITTER (LAPD TRANSMITTER IS CONFIGURED
TO RE-TRANSMIT THE LAPD MESSAGE FRAME REPEATEDLY AT ONE-SECOND INTERVALS)
Start
Write the “LAPD Message frame identification”
octet into the first octet position within the
“Transmit LAPD Message” buffer (Address = 0x86).
Write the PMDL Message into the remaining
portion of the “Transmit LAPD Message” buffer
(from 0x87 to 0xDD).
Specify the type/size of the LAPD Message frame
to be transmitted.
Write in the appropriate value into bits 5 and 6
within the Tx E3 LAPD Configuration Register
Initiate the LAPD Message frame transmission.
LAPD Transmitter will “stuff” the contents of the
PMDL Message (residing within the “Transmit
LAPD Message” buffer).
LAPD Transmitter will read out “stuff” PMDL
Message and encapsulate it into a LAPD Message
frame.
LAPD Transmitter will compute and insert the
FCS value, into the LAPD Message frame.
Specify whether the “outbound” LAPD Message
frame is to be transported via the GC or the NR
byte-fields, within each “outbound” E3 Frame
Enable the LAPD Transmitter
Configure the LAPD Transmitter to repeat transmissions
of the LAPD Message frame at one-second intervals.
LAPD Transmitter will generate a continuous
string of “Flag Sequence” bytes. These bytes will
be transported via either the GC or the NR byte
field (depending upon user’s selection).
LAPD Transmitter will fragment LAPD Message
frame into “octets” and begin to insert these octets into
the GC or NR byte-field (depending upon user’s
selection) into each “outbound” E3 frame.
Complete transmission of LAPD Message frame.
Generate “Completion of Transmission of LAPD
Message frame Interrupt.
Wait One Second. Generate a continuous
string of Flag Sequence Bytes
Figure 176 presents the procedure (in white boxes)
which the user should use in order to transmit a PM-
DL Message via the LAPD Transmitter, when the
LAPD Transmitter is configured to transmit a LAPD
Message frame only once, and then halt transmis-
sion.
389