MT9079
LIU
Trunk
Interface
EC3
to
Control
Port
EC2
EC1
RLOOP
E1 Transmit
MT9079
DSTi
DSTo
TxA
TxB
RxA
RxB
Voice/Data Bus
System Timing
F0i
C4i/C2i
E8ko
E1 Receive
E2i
RCLK
TCLK
Figure 13 - PCM 30 Line Interface Unit (LIU)
MT9079
MT8980D
STon
100Ω
C4i/C2i
DSTi
STin
DSTo
TxA
To Trunk Interface
TxB
100Ω
CSTo
DTA
RxA
RxB
MT8980 µP Interface
MT9079 µP Interface
E2i
+5V
Address
Data
C2
909Ω
C4i
&
Control
C4
MC68302
Figure 14 - Common Channel Signalling Control (Time Slot 16) through the MC68302
the required PCM 30 pseudo-ternary signal; 2) it
converts the received PCM 30 pseudo-ternary signal
to a binary signal; and c) it extracts a data clock form
the receive PCM 30 signal.
location. The BPV counter is cleared by writing zero
to location 1DH first and then writing zero to location
1CH of page 4.
The interrupt vector byte is then cleared by reading
it. This step ensures that interrupts that occurred
when the interface was not initialized will be cleared
before the MT9079 IRQ output is activated. The IRQ
output function is activated by making SPND low.
TAIS is now made high, which indicates to the far
end of the link that this end is functional.
In order to meet network requirements, it is
necessary to control the transmit equalization of the
LIU (EC1 - EC3). This pre-emphasizes the transmit
pulse shape so it can fit within a standard pulse
template at a specific point on the transmit link.
When using a LIU that clocks data in and out with
separate signals, the MT9079 remote loopback can
allow bit errors to occur. This is because the MT9079
does not re-time the looped signal, so phase
differences in the C2 and RCLK clock signals will
impact the transmit data. This problem can be
prevented by implementing the remote loopback in
the LIU and controlling it from a port. Performing the
remote loopback in the LIU also more closely
adheres to network requirements, which state that a
remote loopback should be implemented as close to
the PCM 30 side of the trunk as possible.
It should be noted that Figure 12 is an initialization
example and does not imply that there is a rigid
sequence that must be followed.
PCM 30 Trunk and Timing Interface
Figure 13 shows the MT9079 connection to a generic
Line Interface Unit (LIU). The LIU has three
functions: 1) it converts the framed transmit signal to
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