User`s guide

3: DDCMP Link Conﬁguration Options

DC 900-1343D 57

3.2 Clock Source Option

The clock source option determines the source of the data clock signals for a link. Data

clocking can be provided by the DDCMP software or received from an external source.

3.2.1 External

Simpact recommends the external clock setting for most communications applications

that involve a cable length greater than 25 feet. In the external setting, the clock gener-

ator is disabled. Data clocking must be supplied by an external source such as a modem

or modem eliminator. Receive clocking is input through the receiver timing signal

(EIA-232 pin 17), and transmit clocking is input through the transmitter timing signal

(EIA-232 pin 15). The Freeway 2000/4000 server is factory conﬁgured for external

clocking using a hardware jumper.

3.2.2 Internal

When the internal clock setting is used, the clock signal is generated at the rate speciﬁed

in the data rate option (Section 3.1). The generated clock signal is used for transmit

clocking and is output on the terminal timing signal (EIA-232 pin 24). Receive clocking

is input through the receiver timing signal (EIA-232 pin 17). The transmitter timing

signal (EIA-232 pin 15) is not used. The Freeway 2000/4000 server is factory conﬁgured

for external clocking using a hardware jumper. If you need to set internal clocking on

the Freeway 2000/4000, call the Simpact customer support number given in the Preface.

3.3 Reply Timer Length Option

The reply time is the length of time in seconds that the DDCMP software waits for the

remote station to reply to a transmission. If the remote station does not respond within

the conﬁgured timeout period, the DDCMP software aborts the transmission and

sends the