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DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
87
Bit 3 - Auto Retransmit
This Read/Write bit-field allows the user to configure
the LAPD Transmitter to either transmit the LAPD
Message frame only once or, repeatedly at one-sec-
ond intervals.
Writing a "0" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame
once. Afterwards, the LAPD Transmitter will halt
transmission, until it has commanded to transmit an-
other LAPD Message frame.
Writing a "1" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame re-
peatedly at One-Second intervals. In this configura-
tion, the LAPD Transmitter will repeat its transmission
of the LAPD Message frame until it has been dis-
abled.
Bit 1 - TxLAPD Message Length Select
This Read/Write bit-field permits the user to select
the length of the outbound LAPD Message frame.
Setting this bit-field to "0" configures the outbound
LAPD Message frame to be 76 bytes in length. Set-
ting this bit-field to “1” configures the outbound LAPD
Message frame to be 82 bytes in length.
Bit 0 - TxLAPD Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Transmitter. The LAPD Transmitter
must be enabled before it can be commanded to
transmit a LAPD Message frame (containing a PMDL
message) via the outbound DS3 frames, to the Far-
End Terminal.
Writing a “0" disables the LAPD Transmitter (default
condition). Writing a "1" enables the LAPD Transmit-
ter.
NOTE: For information on the LAPD Transmitter, please see
Section 3.2.3.2.
2.3.5.5
Transmit DS3 LAPD Status and Inter-
rupt Register (DS3 Applications)
Bit 3 - TxDL Start
This Read/Write bit-field allows the user to invoke the
Transmit LAPD Message command. Once the user
invokes this command, the LAPD Transmitter will do
the following:
Read in the PMDL Message from the Transmit
LAPD Message Buffer.
Encapsulate the PMDL Message into a complete
LAPD Message frame by including the necessary
header and trailer bytes (e.g., flag sequence bytes,
SAPI, CR, EA values, etc.).
Compute the frame check sequence word (16 bit
value)
Insert the Frame Check Sequence value into the 2
octet slot after the payload section of the Message.
Proceed to transmit the LAPD Message Frame to
the far end terminal via the outgoing DS3 frames.
Writing a "1" to this bit-field start the transmission of
the LAPD Message Frame, via the LAPD Transmitter.
NOTE: For more information on the LAPD Transmitter,
please see Section 3.2.3.2.
Bit 2 - TxDL Busy
This Read-Only bit-field allows the local P to poll
and determine if the LAPD Transmitter has completed
its transmission of the LAPD Message frame. This
bit-field will contain a "1", if the LAPD Transmitter is
still transmitting the LAPD Message frame to the far-
end terminal. This bit-field will toggle to "0", once the
LAPD Transmitter has completed its transmission of
the LAPD Message frame.
NOTE: For more information on the LAPD Transmitter,
please see Section 3.2.3.2.
Bit 1 - TxLAPD Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Message Frame Transmission
Complete interrupt.
Writing a "0" to this bit-field disables this interrupt.
Writing a "1" to this bit-field enables this interrupt.
Bit 0 - TxLAPD Interrupt Status
This Reset Upon Read bit-field indicates whether or
not the LAPD Message frame Transmission Complete
interrupt has occurred since the last read of this reg-
TXDS3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0
Not Used
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
R/W
RO
R/W
RUR
0
0000
000