Cirrus Logic CDB61880 - Manual (Page 6)

CDB61880
6 DS450DB1
2.3 Operating Mode Selection
The operating mode for the CS61880 can be select-
ed by setting switch S15 to one of the positions
shown in
Figure 4 .
2.4 Line Interface Connections
In both hardware and host modes, the receive line
signals (RTIP/RRING) are connected to the bind-
ing post labeled RXT 0-7 and RXR 0-7. The line
signals from the binding posts are coupled to the
device through two octal transformers (T1 and T9).
The receivers of the device use external resistors to
match the line impedance. These resistors are sock-
eted for ease in changing the line impedance, for in-
ternal or external line impedance matching. During
internal line impedance matching mode, the resis-
tor values are the same (15
Ω) for all modes of op-
eration: E1 75
Ω and E1 120 Ω. During external
line impedance matching mode the receiver resis-
tors need to be change to the values shown in
Table 1 .
The jumpers listed in Table 2 are used to place or
bypass 1 K
Ω protection resistors in series with the
receive line signals (RTIP/RRING). These resis-
tors are used for receiver protection while in exter-
nal line impedance matching mode and should not
be used during internal line impedance matching
mode. To place the 1 K
Ω resistors in series with the
receive line signals, remove the short blocks from
each of the jumpers described in
Table 2 . To by-
pass the 1 K
Ω resistors, place a short block on each
jumper shown in Table 2 .
The transmit line signals (TTIP/TRING) from the
device are coupled to the line binding post (TXT 0-
7 and TXR 0-7) through two octal transformers (T1
and T9). External protection circuitry such as di-
odes or chokes are recommended for protection.
For further information on line protection refer to
Application Note AN34, Secondary Line Protec-
tion for T1 and E1 Line Cards (AN34REV1 SEP
'94).
2.5 TXOE Selection
Jumper J23 is used to enable or High-Z all eight
transmitters in both hardware and host mode. A
shorting block on Jumper J23 places all the trans-
Table 1. External Impedance Resistor Values
E1 75 Ω Ω Ω Ω E1 120 Ω Ω Ω Ω
9.31
Ω
15
Ω
S15
Hardware
Serial Host
Parallel Host
Selects
Hardware Mode
Selects Serial
Host Mode
Selects Parallel
Host Mode
M O D E
S15
Hardware
Serial Host
Parallel Host
S15
Hardware
Serial Host
Parallel Host
M O D E M O D E
Figure 4. Hardware/Host Mode Selection
Table 2. Protection Resistor Selection
Jumper Description
J29 Channel 0 RRING signal
J30 Channel 0 RTIP Signal
J37 Channel 1 RTIP Signal
J38 Channel 1 RRING Signal
J46 Channel 2 RRING Signal
J47 Channel 2 RTIP Signal
J54 Channel 3 RTIP Signal
J55 Channel 3 RRING Signal
J65 Channel 4 RRING Signal
J66 Channel 4 RTIP Signal
J73 Channel 5 RTIP Signal
J74 Channel 5 RRING Signal
J81 Channel 6 RRING Signal
J82 Channel 6 RTIP Signal
J89 Channel 7 RTIP Signal
J90 Channel 7 RRING Signal