82V3012 Datasheet, PDF (10/32 Pages) Integrated Device Technology – T1/E1/OC3 WAN PLL WITH DUAL REFERENCE INPUTS

IDT82V3012
T1/E1/OC3 WAN PLL WITH DUAL REFERENCE INPUTS
2
FUNCTIONAL DESCRIPTION
The IDT82V3012 is a T1/E1/OC3 WAN PLL with dual reference
inputs, providing timing (clock) and synchronization (framing) signals to
interface circuits for multitrunk T1/E1 and STS3/OC3 links. The details
are described in the following sections.
2.1
STATE CONTROL CIRCUIT
The State Control Circuit is an important part in the IDT82V3012. It is
used to control the TIE block and the DPLL block as shown in Figure - 2.
The control is based on the result of Invalid Input Signal Detection and
the logic levels on the MODE_sel0, MODE_sel1, IN_sel and TIE_en
pins.
The IDT82V3012 can be operated in three different modes: Normal,
Holdover and Freerun. The operating mode is selected by the
MODE_sel1 and MODE_sel0 pins, as shown in Table - 1.
Figure - 3 shows the state control diagram. All state changes occur
synchronously on the rising edge of F8o. Three operating modes,
Normal (S1), Holdover (S3) and Freerun (S0) can be switched from one
to another by changing the logic levels on the MODE_sel0 and
MODE_sel1 pins.
TIE Block
Enable/Disable
DPLL Block
Mode Control
Output of the
Invalid Input
State Control Circuit
F8o
Signal Detection
IN_sel TIE_en MODE_sel1 MODE_sel0
Figure - 2 State Control Circuit
Table - 1 Operating Modes Selection
Mode Selection Pins
MODE_sel1
MODE_sel0
0
0
0
1
1
0
1
1
Operating Mode
Normal
Holdover
Freerun
Reserved
Reset *
Auto
TIE
Disable
Auto ^TIE
Disable
S1
Normal
Mode_sel1 = 0
Mode_sel0 = 0
TIE _{DisableT(ITEIEE_nenab=leLA)(TutIoET_IeEnD=isHa)ble}
S0
Freerun
Mode_sel1 = 1
Mode_sel0 = 0
(Valid Input Reference Signal)
TIE Enable (TIE_en = H)
(Valid Input Reference Signal)
TIE Disable (TIE_en = L)
(Invalid Input Reference Signal)
Auto TIE Disable
S3
Holdover
Mode_sel1 = 0
Mode_sel0 = 1
AutoTIE _Disable
AutoTIE _Disable
S2
Auto - Holdover
Mode_sel1 = 0
Mode_sel0 = 0
Auto ^{TIE Disable}
TIE _{ENnoaIbNle_s(TelIET_raenns=ieHnt)}
S4
Short Time Holdover
Mode_sel1 = 0
Mode_sel0 = 0
* Note: After reset, the Mode_sel1 and Mode_sel0 should be initially set to '10' or '00'.
Figure - 3 State Control Diagram
Functional Description
10
IN_sAeluTtoraTnIsEieDnitsable
February 6, 2009