MT9046
Pin Description (continued)
Pin #
45
46
47
48
Name
TDI
TRST
TCK
TMS
Description
Data Sheet
Test Serial Data In (Input).
JTAG serial test instructions and data are shifted in on this pin.
This pin is internally pulled up to V
DD
.
Test Reset (Input).
Asynchronously initializes the JTAG TAP controller by putting it in the
Test-Logic-Reset state. If not used, this pin should be held low.
Test Clock (Input):
Provides the clock to the JTAG test logic. This pin is internally pulled up to
V
DD
.
Test Mode Select (Input).
JTAG signal that controls the state transitions of the TAP
controller. This pin is internally pulled up to V
DD
.
Functional Description
The MT9046 is a Multitrunk System Synchronizer with frequency holdover capability, providing timing (clock) and
synchronization (frame) signals to interface circuits for T1 and E1 Primary Rate Digital Transmission links. Figure 1
is a functional block diagram which is described in the following sections.
Reference Select MUX Circuit
The MT9046 accepts two simultaneous reference input signals and operates on their falling edges. Either the
primary reference (PRI) signal or the secondary reference (SEC) signal can be selected as input to the TIE
Corrector Circuit. The selection is based on the Control, Mode and Reference Selection of the device. See Table 1
and Table 4.
Frequency Select MUX Circuit
The MT9046 operates with one of four possible input reference frequencies (8 kHz, 1.544 MHz, 2.048 MHz or
19.44 MHz). The frequency select inputs (FS1 and FS2) determine which of the four frequencies may be used at
the reference inputs (PRI and SEC). Both inputs must have the same frequency applied to them. A reset (RST)
must be performed after every frequency select input change. See Table 1.
FS2
0
0
1
1
FS1
0
1
0
Input Frequency
19.44 MHz
8 kHz
1.544 MHz
1
2.048 MHz
Table 1 - Input Frequency Selection
Time Interval Error (TIE) Corrector Circuit
The TIE corrector circuit, when enabled, prevents a step change in phase on the input reference signals (PRI or
SEC) from causing a step change in phase at the input of the DPLL block of Figure 1.
During reference input rearrangement, such as during a switch from the primary reference (PRI) to the secondary
reference (SEC), a step change in phase on the input signals will occur. A phase step at the input of the DPLL
would lead to unacceptable phase changes in the output signal.
5
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