
XRT79L71
PRELIMINARY
183
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
NOTE: By default, the Receive Equalizer block will (upon power up) be disabled. Therefore, the user MUST include
enabling the Receive Equalizer block as a part of the start-up/configuration procedure.
4.3.1.4
The Clock and Data Recovery Block
The purpose of the Clock and Data Recovery block (within the Receive DS3/E3 LIU Block) is two-fold.
To acquire and maintain phase-lock with the incoming DS3 or E3 line signal.
To insure that downstream circuitry, (such as the Receive DS3/E3 Framer block) is always provided with a
line-rate clock signal (to use as it timing reference).
Upon power-up, the Clock and Data Recovery block will attempt to acquire phase-lock with the incoming DS3
or E3 line signal. Once the Clock and Data Recovery block has acquired lock with the incoming DS3 or E3
signal, then it will indicate this fact by doing all of the following.
It will set Bit 2 (Receive LOL Defect Declared), within the LIU Alarm StatusRegister, to "0" as depicted below.
It will generate the Change of LOL (Loss of Lock) Defect Condition Interrupt. The XRT79L71 will indicate
that it is generating this interrupt by (a) asserting the Interrupt Request output pin (by toggling it "Low"), and
(b) by setting Bit 2 (Change of LOL Condition Interrupt), within the LIU Interrupt Status Register, to "1" as
depicted below.
LIU Receive Control Register (Address = 0x1305)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Disable
DLOS
Detector
Disable
ALOS Detec-
tor
Unused
LOSMUT
Enable
Receive
Monitor
Mode Enable
Receive
Equalizer
Enable
R/O
R/W
R/O
R/W
0
1
LIU Alarm Status Register (Address = 0x1303)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Digital LOS
Defect
Declared
Analog LOS
Defect
Declared
FL (FIFO
Limit) Alarm
Declared
Receive LOL
Defect
Declared
Receive LOS
Defect
Declared -
Receive
DS3/E3 LIU
Block
Transmit
DMO Condi-
tion
R/O
0