
PRELIMINARY
XRT79L71
308
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
then the user should write a "1" into Bit 3 (Auto Retransmit) within the Transmit E3 LAPD Configuration
Register. This action is depicted below.
STEP 5 - Specify the type of LAPD Message to be transmitted.
At this stage it is necessary to specify the type of LAPD Message, which is to be transmitted. The Transmit
and Receive LAPD Controller blocks within the XRT79L71 are capable of supporting the following standard
types of LAPD Messages.
Test Signal
Idle Signal
CL Path Identification
ITU Path Identification
The ITU Path Identification type of PMDL Message consists of an 82-byte information payload. All of the
remaining standard types of PMDL/LAPD Messages contain 76 byte information payloads. To transmit an 82
byte message (e.g., the ITU Path Identification type of LAPD Message), then the user should set Bit 1
(Transmit LAPD Message Length), within the Transmit E3 LAPD Configuration Register to "1". For all of the
remaining types of LAPD Messages (which are 76 bytes in length), the user should set Bit 1 (Transmit LAPD
Message Length) to "0". This operation is depicted below.
NOTE: This setting will configure the Transmit LAPD Controller to handle LAPD/PMDL messages that contain 76-byte sized
Information Payloads.
To transmit an ITU Path Identification type of PMDL Message, write the value "1" into the Transmit LAPD
Message Length bit-field, as depicted below.
Transmit E3 LAPD Configuration Register (Address = 0x1133)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LAPD
Any
Unused
Auto
Retransmit
Unused
Transmit
LAPD
Message
Length
Transmit
LAPD
Enable
R/W
RO
R/O
R/W
R/O
R/W
0
1
0
X
1
Transmit E3 LAPD Configuration Register (Address = 0x1133)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LAPD
Any
Unused
Auto
Retransmit
Unused
Transmit
LAPD
Message
Length
Transmit
LAPD
Enable
R/W
RO
R/O
R/W
R/O
R/W
0
X
0
1