MT8950 Mitel Networks Corporation, MT8950 Datasheet - Page 11

• Manufacturer Part Number: MT8950
• Description: ISO-CMOS ST-BUS FAMILY Data Codec
• Manufacturer: Mitel Networks Corporation

Codec converts analog signals into the ST-BUS
format while the Data Codec does a similar
conversion for low speed data. The information in
the ST-BUS format can be switched via the Digital
Switch to any of the
subsequently transmitted over the appropriate lines
to the remote destination. At the remote end, the
original signal is regenerated by another
The remote equipment can be part of a local area
network or it may be accessed through leased T1/
CEPT digital lines.
the T1/CEPT leased lines is acquired through the T1/
CEPT interface (MT8976). Full duplex transmission
at 1.544 or 2.048 Mbps is possible with this interface.
The Digital Network Interface Circuit (DNIC), the
MT8972, is capable of providing 160 kbps full duplex
transmission over single telephone pair wiring. This
device can support two 64 kbps channels, allowing
two data codecs to be interfaced to it at the remote
end. Simple, low cost data sets can be constructed
using the data codec and the DNIC.
FROM
DTE
TxD
RxD
AAAA AAAA
AA
AAAA
AA AA
AA AA
AA AA
AAAA AAAA
AA AA
AAAA
AAAA AAAA
AA
AAAA
AA AA
AA AA
AA AA
AAAAAAAAAAAAAAAAA
Scan Point
STi3
STi1
Interface
AAAA AAAA
AAAA AAAA
AAAA AAAA
MT8980
RS-232
Digital Switch
MPU
AAAA AAAA
AAAA AAA
AAAA AAAA
STo0
STo1
AAAA
AAA
Access to remote equipment via
AAAA A A
Line Drivers
C4i
F0i
AA
AA AA
AA AA
AA AA
AA AA
/Receivers
AAAAAAAAAAAAAA
AA
AA AA
AA AA
AA AA
AA AA
AA AA
AAAAAAAAAAAAA
A A
A A
A A
Assignment
Figure 9 - Simplified RS-232 Interface using the Data Codec
AAAA AAAA
AA
AAAA
AA AA
AA AA
AA AA
AA AA
AAAAAAAAAAAA
Channel
Circuit
Circuitry
Timing
AAAA AAAA
other interfaces and
TTL
AAAA
AA
AA AA
AA AA
AA AA
AA AA
AA AA
A
A A
A A
A A
A A
codec.
A simplified interface for transmitting and receiving
RS-232 data signals is illustrated in Figure 9. The
Codec is selected to receive and transmit low speed
data in the NRZ format. The data transmitted by the
terminal equipment in the RS-232 format is inverted
and level shifted to TTL-compatible levels before
being fed into the D
signal is converted into the ST-BUS format and
transmitted via the DSTo output
timeslot when the ST-BUS interface is enabled by
F1i and CA, as dictated by
assignment scheme.
the Codec accepts the 8 bit data arriving on the
incoming ST-BUS stream which is output at the STo1
pin on the MT8980. The data is decoded and the
original signal input at the remote end is regenerated
and output at the D
shifted, inverted and transmitted to the terminal. The
codec in this particular application requires no other
programming. Loading of the Control Register via
the CSTi input is optional.
ground, the Codec will operate in mode 0 (the normal
mode). Note that the SCLK input is tied low. Thus
synchronization pulses will not be transmitted and
10
11
12
1
2
3
4
5
6
7
8
9
CSTi
DSTi
C2i
DSTo
F1i
CA
DF
RxE
D
D
NRZo
V
X
X
SS
ISO-CMOS
1
2
MT8950
X
R
1 input on the Codec.
During this same time period
1 pin.
PRST
SCLK
SPo
D
D
V
SPi
NC
NC
NC
DA
DP
DD
R
R
1
2
If this input is tied to
24
23
22
21
20
19
18
17
16
15
14
13
the system channel
This signal is level
+ 5V
in one channel
MT8950
R = 210 K
C = 1.0 F
The
6-13
R
C