Siemens SIMATIC TIWAY 1 - Manual (Page 62)

CONFIGURING THE HOST COMPUTER PORT
UNILINK HOST ADAPTER 3–4
USER MANUAL
When the synchronous modem operation is selected, the adapter expects the
modem to provide the clocking signals on pins 15 (DB) and 17 (DD). Selecting
synchronous modem operation does not mean that you have selected a
synchronous data link protocol such as the bisynchronous data link protocol.
The adapter supports two asynchronous data link protocols which are described
in further in Paragraph 3.3.
3.2.2 Connection to DTE Equipment
You can also connect a host computer that has a DTE port, such as a
microcomputer, to Port 3 for asynchronous communications by using a null
modem cable. A null modem cable uses 25-pin type “D” connectors and
RS–232–C cable wired as shown in Figure 3–4. Both the adapter and the
attached host see that each is connected to a DCE device. The attaching cable
should not exceed 50 feet in length. You may order this cable from your Siemens
distributor (P/N;VPU–200–3605).
25
1
14
13
25
1
14
13
I002378
Attached Device
DTE
GND
TxD
RxD
RTS
CTS
DSR
GND
DCD
GND
TxD
RxD
RTS
CTS
DSR
GND
DCD
DTR
DTR
UNILINK Host Adapter
DTE
RxCLK–No connection
TxCLK–No connection
Figure 3–4 Cable For Connecting To DTE Equipment (Null
Modem)