User manual

42
Canoga Perkins
3.9 High-Speed RS-422/Mil-Std 188-114C Interfaces
There are three High-Speed RS-422 interface models (-TW, -T22 and -D22) and three High-Speed
Mil-Std 188-114C interface models (-TW8, -T88 and -D88) available.
All can operate up to 20 Mbps. All support only clock and data signals as shown in Table 3-K. Both
the RS-422A and Mil-Std 188-114C are balanced differential electrical signals.
The RS-422A operates between +1 and +4 volts whereas the Mil-Std 188-114C swings between
±3 volts. The termination impedances vary slightly as illustrated in Table 3-L. The two interface
types will communicate with each other but center tap ground jumpers E2 and E3 must be re-
moved from a Mil-Std 188-114C interface (refer to Table 3-M).
The basic differences between the models is the type of physical connectors used for the inter-
face. Table 3-L lists the six interface models with the corresponding source and termination im-
pedances and physical connectors. Table 3-M shows the jumper options available and the factory
default settings for the jumpers.
Table 3-K. TwinAx and BNC Supported Signals
Signal Full Name Direction
TxD Transmit Data To Modem
RxD Receive Data From Modem
SCR Serial Clock Receive From Modem
SCT Serial Clock Transmit From Modem
SCTE External Clock Transmit To Modem
Table 3-L. Model Characteristics
Model Electrical Physical Driver Driver Termination
Interface Interface Impedance Impedance Impedance
Type Type Figure /
Table
TW RS-422A 4 TwinAx Fig. 3-6 <100 Ohms 100 Ohms ±10%
TW8 Mil-Std 4 TwinAx Fig. 3-6 <100 Ohms 78 Ohms ±10%
118-114C
T22 RS-422A 5 TwinAx Fig. 3-7 <100 Ohms 100 Ohms ±10%
T88 Mil-Std 5 TwinAx Fig. 3-7 <100 Ohms 78 Ohms ±10%
188-114C
D22 RS-422A DC-37 Tbl. 3-N <100 Ohms 100 Ohms ±10%
D88 Mil-Std DC-37 Tbl. 3-N <100 Ohms 124 Ohms ±10%
188-114C