XR72L52 Datasheet, PDF (245/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L52
REV. 1.0.1
Whenever the XRT72L52 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (Int) by driving this pin "Low".
• It will set Bit 6 (LOS Interrupt Status) within the RxDS3 Interrupt Status register to “1”, as illustrated below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
1
0
0
0
0
0
0
Whenever the user’s system encounters the Change of LOS on Receive Interrupt, then it should do the follow-
ing.
1. It should determine the current state of the LOS condition. Recall, that this interrupt can generated, when-
ever the XRT72L52 Framer declares or clears the LOS defects. Hence, the current state of the LOS defect
can be determined by reading the state of Bit 6 (RxLOS), within the RxDS3 Configuration & Status Regis-
ters, as illustrated below.
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
RxAIS
RO
0
BIT 6
RxLOS
RO
1
BIT 5
RxIdle
RO
0
BIT 4
RxOOF
RO
0
BIT 3
Reserved
RO
X
BIT 2
Framing On
Parity
R/W
0
BIT 1
FSync
Algo
R/W
0
BIT 0
MSync
Algo
R/W
0
If the LOS State is TRUE
1. It should transmit a FERF (Far-End Receive Failure) to the Remote Terminal Equipment. The XRT72L52
Framer IC automatically supports this action via the FERF-upon-LOS feature.
2. It should transmit the appropriate FEAC Message (per Bellcore GR-499-CORE), to the Remote Terminal,
indicating that a Loss of Signal condition has been declared.
If the LOS State is FALSE
1. It should cease transmitting a FERF indicator to the Remote Terminal Equipment. The XRT72L52 Framer
IC automatically supports this action via the FERF-upon-LOS feature.
2. It should transmit the appropriate FEAC Message (per Bellcore GR-499-CORE), to the Remote Terminal
Equipment, indicating that the Loss of Signal condition has been cleared.
4.3.6.2.2 The Change of State on Receive OOF Interrupt
If the Change of State on Receive OOF (Out-of-Frame) Interrupt is enabled, then the XRT72L52 Framer IC will
generate an interrupt in response to either of the following conditions.
1. When the XRT72L52 Framer IC declares an OOF (Out of Frame) condition, and
2. When the XRT72L52 Framer IC clears the OOF (Out of Frame) condition.
Conditions causing the XRT72L52 Framer IC to declare an OOF condition
• If the Receive DS3 Framer block (within the XRT72L52 Framer IC) detects at least either 3 or 6 F-bit errors,
in the last 16 F-bits.
Conditions causing the XRT72L52 Framer IC to clear the OOF condition.
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