XRT72L56 Datasheet, PDF (235/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
XRT72L56
REV. P1.1.2
PMON PARITY ERROR EVENT COUNT REGISTER - LSB (ADDRESS = 0X55)
BIT 7
BIT 6
BIT 5
BIT 4
0
0
0
0
When the µP reads these registers, it will read in the
number of parity-bit errors that have been detected by
the Receive DS3 Framer block, since the last time
these registers were read. These registers are reset
upon read.
NOTE: When the Framing with Parity option is selected, the
Receive DS3 Framer block will declared an OOF condition if
P-bit errors were detected in two out of 5 consecutive DS3
M-frames.
3.3.2.6.2 CP-Bit Checking/Options
CP-bits are very similar to P-bits except for the follow-
ing.
1. CP-bits are used to permit performance monitor-
ing over an entire DS3 path (e.g., from the source
BIT 3
BIT2
BIT 1
BIT 0
0
0
0
0
terminal) through any number of mid-network ter-
minals to the sink terminal).
2. P-bits are used to permit performance monitoring
of a DS3 data stream, as it is transmitted from
one terminal to an adjacent terminal.
How CP-Bits are Processed
The following section describes how the CP-bits are
processed at three locations.
• The Source Terminal Equipment
• The Mid-Network Terminal Equipment
• The Sink Terminal Equipment
Figure_62 presents a simple illustration of the loca-
tions of these three types of Terminal Equipment,
within the Wide-Area Network.
FIGURE 82. A SIMPLE ILLUSTRATION OF THE LOCATIONS OF THE SOURCE, MID-NETWORK AND SINK TERMINAL
EQUIPMENT (FOR CP-BIT PROCESSING)
CCuustsotommerer
PPrermemisiesses
EEqquuipipmmenent _t
SSouourcrece
TTeremrmininaal _l
EEqquuipipmmenent _t
MMidid-N-Netewtworokrk
TTeremrmininalal
EEqquuipipmmenent _t
SSininkk
TTeremrmininalal
EEqquuipipmmenent _t
CCuustsotmomerer
PPrermemisiesses
EEqquuipipmmenent _t
The Wide Area Network
NOTE: The use of the terms Source and Sink Terminal
Equipment are used to simplify this discussion of CP-Bit
Processing. In reality, the Source Terminal Equipment (in
Figure_62) will also function as the Sink Terminal Equip-
ment (for DS3 traffic traveling in the opposite direction).
Likewise, the Sink Terminal Equipment (in Figure_62) will
also function as the Source Terminal Equipment.
Processing at the Source Terminal Equipment
The Source Terminal Equipment (located at one edge
of the wide-area network) will typically receive its DS3
payload data from some Customer Premise Equip-
ment (CPE). As the Source Terminal Equipment re-
ceives this data from the CPE, it will compute the
even-parity value over all bits within a given outbound
DS3 frame. The Terminal Equipment will then insert
this even parity value into both of the P-bit fields and
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