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PRELIMINARY
FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L54
REV. P1.1.2
98
Bit 6 - RxAbort
This Read-Only bit-field indicates whether or not the
LAPD Receiver is currently detecting an abort se-
quence (e.g., a string of 7 consecutive "1’s").
This bit-field is set to "1" if the LAPD Receiver is cur-
rently detecting an abort sequence in the incoming
LAPD Channel. Conversely, this bit-field is set to "0"
if the LAPD Receiver has not detected an abort se-
quence, since the last read of this register.
Bit 5, 4 - RxLAPD Type[1:0]
These two Read-Only bit-fields combine to indicate
the type and size of LAPD Message frame that has
been received by the LAPD Receiver. The following
table relates the contents of these bit-fields to the
LAPD Message type/size.
Bit 3 - RxCR Type
This Read-Only bit-field indicates the state of the C/R
bit-field, within octet # 2 of the most recently received
LAPD Message frame.
Bit 2 - RxFCS Error
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected an FCS (Frame Check
Sequence) error, in the most recently received LAPD
Message frame. This bit-field is set to "0" if the LAPD
Receiver does not detect an FCS error in this LAPD
Message frame. Conversely, this bit-field is set to "1"
if the LAPD Receiver does detect an FCS error in this
LAPD Message frame.
N
OTE
:
For a more detailed discussion on the LAPD
Receiver's handling of the FCS bytes, please see Section
4.3.3.
Bit 1 - EndOfMessage
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 con-
tains a new PMDL message that needs to be read
and processed.
This bit-field is cleared (to "0") upon reading this reg-
ister.
Bit 0 - Flag Present
The LAPD Receiver will assert this read-only bit-field
when it is currently detecting the Flag Sequence octet
(0x7E) in the incoming LAPD channel (e.g., either the
GC or the NR byte-field, within each E3 frame). The
LAPD Receiver will negate this bit-field when it is no
longer receiving the Flag Sequence octet in the in-
coming LAPD channel.
2.4.4.9
Receive E3 Service Bits Register (E3,
ITU-T G.751)
Bit 1 - RxA (A-Bit)
This Read-Only bit-field reflects the state of the “A”
bit-field, within the most recently received E3 frame.
Bit 0 - RxN (N-Bit)
This Read-Only bit-field reflects the state of the “N”
bit-field, within the most recently received E3 frame.
2.4.5
Transmit DS3 Configuration Registers
2.4.5.1
Transmit DS3 Configuration Register
(DS3 Applications)
R
X
LAPDT
YPE
[1:0]
LAPD M
ESSAGE
F
RAME
T
YPE
PMDL M
ESSAGE
S
IZE
(I
NFORMATION
S
ECTION
)
00
CL Path Identification Type
76 Bytes
01
Idle Signal Identification Type
76 Bytes
10
Test Signal Identification Type
76 Bytes
11
ITU-T Path Identification Type
82 Bytes
RXE3 SERVICE BIT REGISTER (ADDRESS = 0X1A)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
RxA
RxN
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0