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Chapter 2
Installing the KF3
RS 232C Cabling
Considerations
Signal
Chassis Ground
Transmit Data
Receive Data
Request to Send
Clear to Send
Data Set Ready
Signal Ground
Data Carrier Detect
Data Terminal Ready
2 8
Cabling for the RS-232C connector of the KF3 will vary depending on
your application. The pinouts for this connector are given in Table 2.B.
Table 2.B
RS 232C Connector Pinouts
Abbreviation
Direction
-
-
TXD
Output
RXD
Input
RTS
Output
CTS
Input
DSR
Input
GND
-
DCD
Input
DTR
Output
Pin No.
Meaning
1
The cable shield must be connected to chassis ground at one
end only.
2
RS 232C serialized data output from the module.
3
RS 232C serialized data input to the module.
4
A request from the module to the modem to prepare to
transmit. With full duplex protocol, RTS is always asserted.
With half duplex protocol, it is turned on when the module has
permission to transmit, otherwise it is off.
5
A signal from the modem to the module that indicates the
carrier is stable and the modem is ready to transmit. The
module will not transmit until CTS is on. If CTS is turned off
during transmission, the module will stop transmitting until
CTS is restored.
6
A signal from the modem to the module that indicates the
phone is off hook. It is the modem's answer to DTR. The
module will not transmit or receive unless DSR is on. If
the modem does not control DSR properly, DSR must be
jumpered to a high signal at the module. (It can be jumpered
to DTR.)
7
Signal ground - a reference point for the data signals.
8
A signal from the modem to the module to indicate that the
carrier from another modem is being sensed on the phone
line. It will not be asserted unless the phone is off hook.
Data will not be received by the KF3 unless DCD is on. With
full duplex protocol, the module will not transmit unless DCD
is on. If the modem does not control DCD properly, DCD must
be jumpered to DTR at the module.
20
A signal from the module to the modem to connect to the
phone line (i.e., pick up the phone"). The module will assert
DTR all the time except during the phone hang up sequence.
Modems built to North American standards will not respond
to DTR until the phone rings. The KF3 module will not work
correctly with modems which always pick up the phone upon
receiving DTR, whether the phone is ringing or not.
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