
á
XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
397
plished by periodically reading the PMON Framing
Bit/Byte Error Event Count Registers (Address = 0x52
and 0x53). The byte format of these registers are
presented below.
6.3.2.5
The RxOOF and RxLOF output pin.
The user can roughly determine the current framing
state that the Receive E3 Framer block is operating in
by reading the logic state of the RxOOF and the Rx-
LOF output pins.
Table 85 presents the relationship
between the state of the RxOOF and RxLOF output
pins, and the Framing State of the Receive E3 Framer
block.
6.3.2.6
E3 Receive Alarms
6.3.2.6.1
The Loss of Signal (LOS) Alarm
Declaring an LOS Condition
The Receive E3 Framer block will declare a Loss of
Signal (LOS) Condition, when it detects 32 consecu-
tive incoming “0’s” via the RxPOS and RxNEG input
pins or if the ExtLOS input pin (from the XRT7300
DS3/E3/STS-1 LIU IC) is asserted. The Receive E3
Framer block will indicate that it is declaring an LOS
condition by.
Asserting the RxLOS output pin (e.g., toggling it
“High”).
Setting Bit 4 (RxLOS) of the Rx E3 Configuration &
Status Register to “1” as depicted below.
The Receive E3 Framer block will generate a
Change in LOS Condition interrupt request. Upon
generating this interrupt request, the Receive E3
Framer block will assert Bit 1 (LOS Interrupt Status
within the Rx E3 Framer Interrupt Status Register -
1, as depicted below.
Clearing the LOS Condition
The Receive E3 Framer block will clear the LOS con-
dition when it encounters a stream of 32 bits that
does not contain a string of 4 consecutive zeros.
TABLE 85: THE RELATIONSHIP BETWEEN THE LOGIC STATE OF THE RXOOF AND RXLOF OUTPUT PINS, AND THE
FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK
RXLOF
RXOOF
FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK
00
In Frame
01
OOF Condition (The Receive E3 Framer block is operating in the 3ms OOF period).
10
Invalid
11
LOF Condition
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RORO
RO
RORORORO
0
0010
000
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT 2BIT 1BIT 0
Not Used
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RUR
0
0000
010