XRT72L50 Datasheet, PDF (388/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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Transmit E3 LAPD Configuration Register (Address = 0x33)
BIT 7
RO
0
BIT 6
BIT 5
Not Used
RO
RO
0
0
BIT 4
RO
0
BIT 3
Auto
Retransmit
R/W
X
BIT2
Not Used
RO
0
BIT 1
TxLAPD
Msg Length
R/W
X
BIT 0
TxLAPD
Enable
R/W
X
The relationship between the contents of bit-field 1 and the LAPD Message size is given in Table 74.
TABLE 74: RELATIONSHIP BETWEEN TXLAPD MSG LENGTH AND THE LAPD MESSAGE SIZE
TXLAPD MESSAGE LENGTH
0
1
LAPD MESSAGE LENGTH
LAPD Message size is 76 bytes
LAPD Message size is 82 bytes
NOTE: The Message Type selected must correspond with the contents of the first byte of the Information (Payload) portion,
as presented in Table 73.
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.
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TxE3 Configuration Register (Address = 0x30)
BIT 7
RO
0
BIT 6
Not Used
RO
0
BIT 5
RO
0
BIT 4
TxDL
in NR
R/W
X
BIT 3
Not Used
RO
0
BIT 2
TxAIS
Enable
R/W
0
BIT 1
TxLOS
Enable
R/W
0
BIT 0
TxMARx
R/W
0
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.
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