MT9044AP1 Zarlink Semiconductor, Inc., MT9044AP1 Datasheet - Page 10

• Manufacturer Part Number: MT9044AP1
• Description: Framer: Framer Circuit: T1/E1/OC3 System Synchronizer
• Manufacturer: Zarlink Semiconductor, Inc.

Guard Time Circuit
The GTi pin is used by the Automatic/Manual Control State Machine in the MT9044 under either Manual or
Automatic control. The logic level at the GTi pin performs two functions, it enables and disables the TIE Corrector
Circuit (Manual and Automatic), and it selects which mode change takes place (Automatic only).
Applications - Guard Time section.
For both Manual and Automatic control, when switching from Primary Holdover to Primary Normal, the TIE
Corrector Circuit is enabled when GTi=1, and disabled when GTi=0.
Under Automatic control and in Primary Normal Mode, two state changes are possible (not counting Auto-
Holdover). These are state changes to Primary Holdover or to Secondary Normal. The logic level at the GTi pin
determines which state change occurs. When GTi=0, the state change is to Primary Holdover. When GTi=1, the
state change is to Secondary Normal.
Master Clock
The MT9044 can use either a clock or crystal as the master timing source. For recommended master timing
circuits, see the Applications - Master Clock section.
Control and Modes of Operation
The MT9044 can operate either in Manual or Automatic Control. Each control method has three possible modes of
operation, Normal, Holdover and Freerun.
As shown in Table 3, Mode/Control Select pins MS2 and MS1 select the mode and method of control.
MS2
MANUAL
Control
0
0
1
1
AUTO
Table 3 - Operating Modes and States
Table 2 - Input Reference Selection
MS1
0
1
0
1
RSEL
Zarlink Semiconductor Inc.
MANUAL
MANUAL
MANUAL
Control
0
1
0
1
AUTO
MT9044
10
State Machine Control
State Machine Control
Input Reference
Reserved
HOLDOVER
FREERUN
NORMAL
SEC
PRI
Mode
Data Sheet
See the