XRT72L50
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SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
375
The relationship between the contents of bit-field 1 and the LAPD Message size is given in
Table 74.NOTE: The Message Type selected must correspond with the contents of the first byte of the Information (Payload) portion,
as presented in
STEP 4 - Specifying which byte-field (within the E3 frame) that the LAPD Message frame octets are to
be transported on.
The Transmit E3 Framer block allows the user to transport the LAPD Message frame octets via either the NR
byte or the GC byte-field, within each Outbound E3 frame. The user makes this selection by writing the
appropriate value to bit-field 4 (DLinNR), within the Tx E3 Configuration Register, as depicted below.
)
If the user writes a “0” into this bit-field, then the LAPD Transmitter will transmit the comprising octets of the
Outbound LAPD Message frame via the GC byte field. Additionally, the Transmit E3 Framer block will insert
the contents of the TxNR Byte Register (Address = 0x37) into the NR byte of each Outbound E3 frame.
Conversely, if the user writes a “1” into this bit-field, then the LAPD Transmitter will transmit the Outbound
LAPD Message frame octets via the NR byte-field, within each Outbound E3 frame. Additionally, the Transmit
E3 Framer will insert the contents of the Tx GC Byte Register (Address = 0x35) into the GC byte-field of each
Outbound E3 frame.
STEP 5 - Specify whether the LAPD Transmitter should transmit the LAPD Message frame only once, or
an indefinite number of times at One-Second intervals.
The Transmit E3 HDLC Control block allows the user to configure the LAPD Transmitter to transmit this LAPD
Message frame only once, or an indefinite number of times at One-Second intervals. The user implements this
configuration by writing the appropriate value into Bit 3 (Auto Retransmit) within the Tx E3 LAPD Configuration
Register (Address = 0x33), as depicted below.
Transmit E3 LAPD Configuration Register (Address = 0x33)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT2
BIT 1BIT 0
Not Used
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
RO
R/W
RO
R/W
00
X
0
XX
TABLE 74: RELATIONSHIP BETWEEN TXLAPD MSG LENGTH AND THE LAPD MESSAGE SIZE
TXLAPD MESSAGE LENGTH
LAPD MESSAGE LENGTH
0
LAPD Message size is 76 bytes
1
LAPD Message size is 82 bytes
TxE3 Configuration Register (Address = 0x30)
BIT 7BIT 6BIT 5
BIT 4BIT 3BIT 2BIT 1BIT 0
Not Used
TxDL
in NR
Not Used
TxAIS
Enable
TxLOS
Enable
TxMARx
RO
R/W
RO
R/W
00
0
X
0
000