Compaq 3000 - Manual (Page 23)

Chapter 1. Product Overview
EK–SMCPQ–UG. C01 1–11
Figure 1–7 Host I/O Module
SHR-1036
Host Out
Host In
CTR
UPS
The front panel of the host I/O module contains two 68-pin VHDCI SCSI con-
nectors and two 9-pin D connectors. The SCSI connectors provide the SCSI bus
connections between the adapter in the host system and the controller(s) in the
Shelf. One of the 9-pin D connectors interfaces the UPS status signals to the
controller. The other provides a serial connection between its respective control-
ler, the Shelf, and the SWCC configuration/maintenance PC.
The high-density SCSI connectors on the Host I/O module are designated Host In
(bottom connector) and Host Out (top connector). Host In provides the SCSI
connection for a one-to-four expansion shelf cabinet installation. Cable connec-
tions to multiple storage shelves are made through Trilink adapters.
In addition to the front panel connectors, the Host I/O module contains three pas-
sive differential SCSI bus terminators that terminate the SCSI bus from the host
system. Termination is automatically disabled when a cable is connected to the
Host Out connector. The UPS serial connector on the host I/O module (desig-
nated CTR 0 and CTR 1) provides shelf status information to the UPS.
NOTE
If you have only one SCSI cable connection to the
host I/O module, you must connect the cable to
the
Host In connector. Do not use any external
bus termination. The Host Out connector on the
module is used for mid-bus connections in a mul-
tiple-host system configuration.