ASCOM Ascotel 2025 System Manual page 845

ascom Ascotel 2025/2045/2065
A null modem cable (link cable) must be used when connecting equipment of sim-
ilar type: DTE – DTE (e.g. PC ® PC). The null modem cable is crossed.
The DCD signal should only be used if a DCE is connected with a DTE.
DCD is activated by the DCE once the connection to the DTE is established.
Flow Control
Depending on the set mode, the data flow is controlled differently by the equip-
ment involved. The most common modes are SW and RTS / CTS.
SW Mode
This mode is also known as a software handshake.
The data flow is controlled by the data receiving equipment. The data receiving
equipment sends an SW signal over the data line as soon as its input memory is
full, and an SW signal as soon as it is ready to receive again.
SW requires only a three-wire connection for signals RxD, TxD and SGND.
Drawback: The data transmitting equipment cannot tell whether or not a receiv-
ing equipment is connected.
RTS / CTS Mode
This mode is also known as a hardware handshake.
The two equipment involved use the RTS and CTS signals to indicate that they are
ready to send and to receive, each signal being transmitted over a separate sig-
nalling line.
Advantage: Data exchange cannot take place if there is no equipment ready to
receive, e.g. no data will be sent to a printer if the printer is switched off or out
of paper.
Note:
To exclude any transmission errors, always operate the printer on Asco-
tel in RTS / CTS mode.
4.74 Cabling Interfaces HBT_20321104_04/B0_en