XRT72L13 Datasheet, PDF (345/370 Pages) Exar Corporation – M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

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PRELIMINARY
XRT72L13
M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC
REV. P1.0.6
Servicing the “Change of State” on Receive Idle
Interrupt
Whenever the XRT72L13 Framer IC detects this in-
terrupt, it will do all of the following.
• It will assert the “Interrupt Request” Output pin
(INT*) by driving it “LOW”.
• It will set Bit 4 (Idle Interrupt Status), within the “Rx
DS3 Interrupt Status” Register to “1”, as indicated
below.
•
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
CP-Bit Error
Interrupt
Status
RUR
0
BIT 6
LOS
Interrupt
Status
RUR
0
BIT 5
AIS
Interrupt
Status
RUR
0
BIT 4
Idle Interrupt
Status
RUR
1
BIT 3
FERF
Interrupt
Status
RUR
0
BIT 2
AIC
Interrupt
Status
RUR
0
BIT 1
OOF
Interrupt
Status
RUR
0
BIT 0
P-Bit Error
Interrupt
Status
RUR
0
Whenever the Terminal Equipment encounters the
“Change in Idle Condition Receive” Interrupt, it should
do the following.
1. It should determine the current state of the “Idle”
condition. Recall, that this interrupt can gener-
ated, whenever the XRT72L13 Framer declares
or clears the Idle condition. Hence, the user can
determine the current state of the Idle condition
by reading the state of Bit 5 (RxIdle), within the
“RxDS3 Configuration & Status” Registers, as
illustrated below
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
BIT 1
FSync
Algo
RO
0
BIT 0
MSync
Algo
RUR
0
4.3.6.2.5 The “Change of State” of Receive
FERF Interrupt
If the “Change of State on Receive FERF” Interrupt is
enabled, then the XRT72L13 Framer IC will generate
an interrupt in response to either of the following con-
ditions.
1. When the XRT72L13 Framer IC detects the
FERF indicator, in the “incoming” DS3 data
stream, and
2. When the XRT72L13 Framer IC no longer detects
the FERF indicator, in the “incoming” DS3 data
stream.
Conditions causing the XRT72L13 Framer IC to
declare an FERF (Far-End-Receive Failure) condi-
tion
• If the Receive DS3 Framer block (within the
XRT72L13 Framer IC) detects some “incoming”
DS3 frames with both of the “X” bits set to “0”.
Conditions causing the XRT72L13 Framer IC to
clear the FERF condition.
• Whenever, the “Receive DS3 Framer” block starts
to detect some “incoming” DS3 frames, in which the
“X” bits are not set to “0”.
Enabling and Disabling the “Change of State on
Receive FERF Interrupt:
The user can enable or disable the “Change of State
on Receive FERF” Interrupt, by writing the appropri-
ate value into Bit 3 (FERF Interrupt Enable) within the
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