Instructions

UM-0085-B09 DT80 Range User Manual Page 392
RG
RS-232
Signals
The following table lists the standard RS-232 pinouts for both 9-pin (DE-9) and 25-pin (DB-25) DCE and DTE interfaces.
Normally the DTE (DT80, computer) device’s connector is male and the DCE (modem) device’s connector is female.
Signal
Function
Direction
DE-9 Pin
DB-25 Pin
DCD
Data Carrier Detect
DTE ← DCE
1
8
RXD
Receive Data
DTE
←
DCE
2
3
TXD
Transmit Data
DTE → DCE
3
2
DTR
Data Terminal Ready
DTE → DCE
4
20
GND
Signal Ground
5
7
DSR
Data Set Ready
DTE ← DCE
6
6
RTS
Request To Send
DTE → DCE
7
4
CTS
Clear To Send
DTE ← DCE
8
5
RI
Ring Indicator
DTE ← DCE
9
22
Table 23: RS-232 Pinouts
Figure 174: RS-232 Pin Numbering
Cables
Host Port null modem cable
For applications where a DTE is connected to another DTE (e.g. a DT80 is connected to a host computer):
• The RXD and TXD signals must be "crossed over" so that one device's TXD is connected to the other device's
RXD.
• The "Request To Send" output changes its meaning to "Clear To Send Output" (i.e. a device sets it active when
it is able to receive data). This allows hardware flow control to operate in both directions.
• DCD, DTR, DSR and RI are not normally used.
The following cable (dataTaker product code IBM-6) is used to connect a PC serial port to the DT80 host RS232 port.
The cable is terminated by a female DE-9 connector at each end. The wiring is symmetrical, i.e. the cable can be
connected either way around.
Figure 175: RS-232 Null Modem Cable (IBM-6)
1 DCD
2 RXD
3 TXD
4 DTR
5 GND
6 DSR
7 RTS
8 CTS
9 RI
1 DCD
2 RXD
3 TXD
4 DTR
5 GND
6 DSR
7 RTS
8 CTS
9 RI
Female DE-9
Female DE-9
Male DE-9
Female DE-9