
XRT7250
DS3/E3 FRAMER IC
á
REV. 1.1.1
92
2.3.6.3
Transmit E3 LAPD Status and Interrupt
Register (E3, ITU-T G.832)
Bit 3 - TxDL Start
This Read/Write bit-field allows the user to command
the LAPD Transmitter to do the following.
Scan through the PMDL Message, within the Trans-
mit LAPD Message buffer, and search for a string of
five (5) consecutive "1’s". The LAPD Transmitter
will then insert (or stuff) a "0" into the PMDL Mes-
sage data, immediately following any string of 5
consecutive "1’s".
Read in this stuffed PMDL Message from the Trans-
mit LAPD Message buffer, and encapsulate it into a
LAPD Message frame.
Fragment the resulting LAPD Message frame into
octets.
Insert these octets into either the GC byte-field or
the NR byte-field (depending upon the user's selec-
tion) in each outbound E3 frame.
A "0" to "1" transition, in this bit-field commands the
LAPD Transmitter to initiate the above-mentioned
procedure.
NOTE: Once the user has commanded the LAPD Transmit-
ter to start transmission, the LAPD Transmitter will repeat
the above-mentioned process once each second and will
insert flag sequence octets into the outbound LAPD chan-
nel, during the idle periods between transmissions.
Bit 2 - TxDL Busy
This Read-Only bit-field allows the user to poll or
monitor the status of the LAPD Transmitter to see if it
has completed its transmission of the LAPD Message
frame. The LAPD Transmitter will set this bit-field to
"1", while it is in the process of transmitting the LAPD
Message frame. However, the LAPD Transmitter will
clear this bit-field to "0" once it has completed its
transmission of the LAPD Message frame.
Bit 1 - TxLAPD Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Message frame Transmission Com-
plete 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 allows the user to de-
termine if the LAPD Message Frame Transmission
Complete interrupt has occurred since the last read of
this register. If this bit-field contains a "1" then the
LAPD Message Frame Transmission Complete inter-
rupt has occurred since the last read of this register.
Conversely, if this bit-field contains a "0" then it has
not.
2.3.6.4
Transmit E3 GC Byte Register (E3, ITU-
T G.832)
This Read/Write byte-field allows the user to specify
the contents of the GC byte-field in each outbound E3
frame.
NOTE: The contents of this register is ignored, if the LAPD
Transmitter is enabled and has been configured to insert
the comprising octets of an outbound LAPD Message
frame into the GC byte-field of each outbound E3 frame
(e.g., if DLinNR = "0").
2.3.6.5
Transmit E3 MA Byte Register (E3, ITU-
T G.832)
TXE3 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
00
000
TXE3 GC BYTE REGISTER (ADDRESS = 0X35)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0
TxGC[7:0]
R/W
00
000