
XRT72L54
FOUR CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.2
243
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 XRT72L54 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 illus-
trated below
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 XRT72L54 Framer IC will generate
an interrupt in response to either of the following con-
ditions.
1. When the XRT72L54 Framer IC detects the
FERF indicator, in the incoming DS3 data stream,
and
2. When the XRT72L54 Framer IC no longer detects
the FERF indicator, in the incoming DS3 data
stream.
Conditions causing the XRT72L54 Framer IC to
declare an FERF (Far-End-Receive Failure) condi-
tion
If the Receive DS3 Framer block (within the
XRT72L54 Framer IC) detects some incoming DS3
frames with both of the “X” bits set to “0”.
Conditions causing the XRT72L54 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 appropriate
value into Bit 3 (FERF Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
Setting this bit-field to “1” enables this interrupt. Con-
versely, setting this bit-field to “0” disables this inter-
rupt.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 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
RURRUR
RUR
RURRUR
00
010
000
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RUR
00
000
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
00
000