Sun Microsystems Interface Adapter, User Manual

Page: 49 / 66

29
A P P E N D I X
B
Null Modem Cable Requirements
A synchronous null modem cable is a specially configured cable that simulates
modems that are connected back-to-back. When the distance between the two host
systems is not great, you may be able to use a null modem cable instead of a
synchronous modem or a synchronous modem eliminator.
The maximum distance a null modem cable can work is determined by the
specification for your serial port interface.
There are two steps you must perform to use a null modem cable for machine
supplied clocking:
■
Run
hsip_init
(see “Configuring Internal or External Clocking” on page 30 ) so
that the Sun system, in the absence of a synchronous modem, supplies clocking
on the serial line.
■
Build or configure the cable for the null modem.
Note –
You must run
hsip_init
each time you reboot your system.
The following topics are included in this appendix:
■
“Configuring Internal or External Clocking” on page 30
■
“Building the Null Modem Cable” on page 30