XRT72L52
REV. 1.0.1
xr
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
62
Bit 6 - RxAbort (Receive Abort Sequence)
This Read-Only bit-field indicates whether or not the LAPD Receiver has detected the occurrence of an Abort
Sequence (e.g., a string of seven or more consecutive "1’s") from the remote LAPD Transmitter. A "0" in this
bit-field indicates that no Abort-Sequence has been detected. A "1" in this bit-field indicates that the Abort-Se-
quence has been detected.
N
OTE
:
For more information on the LAPD Receiver, refer to
Section 4.3.3.2
.
Bits, 5 and 4 - RxLAPDType[1:0]
These two Read Only bit-fields combine to indicate the type of LAPD Message frame that has been received
by the LAPD Receiver. The relationship between these two bit-fields and the LAPD Message Type follows:
Bit 3 - RxCR (Command/Response) Type
This Read Only bit field indicates the value of the C/R (Command/Response) bit-field of the latest received
LAPD Message.
Bit 2 - Rx FCS (Frame Check Sequence) Error
This Read-Only bit-field indicates whether or not the LAPD Receiver has detected a Frame Check Sequence
(FCS) error in the most recently received LAPD Message Frame. A "0" in this bit-field indicates that the FCS
for the latest received LAPD Message Frame is correct. A "1" in this bit-field indicates that the FCS for the lat-
est received LAPD Message Frame is incorrect.
N
OTE
:
For more information on the LAPD Receiver, refer to
Section 4.3.3.2
.
Bit 1 - End Of Message
This Read-Only bit-field indicates whether or not the LAPD Receiver has completed its reception of the latest
incoming LAPD Message frame. The local μP can poll the progress of the LAPD Receiver by periodically
reading this bit-field.
The LAPD Receiver will assert this read-only bit-field, when it has received a complete LAPD Message frame.
This bit-field, along with the Receipt of New LAPD Message frame interrupt, serves to inform the local μP that
the Receive LAPD Message buffer contains a new PMDL message that needs to be read and processed.
This bit-field is cleared (to "0") when the LAPD receiver starts receiving a new LAPD frame. (The EOM bit goes
“Low” once a valid header is received.).
A "0" in this bit-field indicates that the LAPD Receiver is still receiving the latest message from the remote
LAPD Transmitter. A "1" in this bit-field indicates that the LAPD Receiver has finished receiving the complete
LAPD Message Frame.
Bit 0 - Flag Present
This Read-Only bit-field indicates whether or not the LAPD Receiver has detected the occurrence of the Flag
Sequence byte (0x7E) within the inbound LAPD channel (e.g., the DL bits in DS3 applications). A "0" in this
bit-field indicates that the LAPD Receiver does not detect the occurrence of the Flag Sequence byte. A "1" in
this bit-field indicates that the LAPD Receiver does detect the occurrence of the Flag Sequence byte.
N
OTE
:
For more information on the LAPD Receiver, refer to
Section 4.3.3.2
.
2.3.3
Receive E3 Framer Configuration Registers (ITU-T G.832)
N
OTE
:
The default register values shown below are after the operating mode is set to G.832 Bit mode. These are different
from the power-up default values.
R
X
LAPDT
YPE
[1:0]
M
ESSAGE
T
YPE
M
ESSAGE
LENGTH
B
IT
5
B
IT
4
0
0
CL Path Identification
76 Bytes
0
1
Idle Signal Identification
76 Bytes
1
0
Test Signal Identification
76 Bytes
1
1
ITU-T Path Identification
82 Bytes