
Hytec Electronics Ltd 8901-CC/UTM/G/x/1.1
Page 3
1.INTRODUCTION
The Hytec 8901-CC is a DIN-Rail mounted board which allows voltage free contacts to be sensed by
connection to a VME64X carrier board. It connects to the transition board using a 50-way SCSI cable.
•50-way terminal connection to plant equipment.
•50-way SCSI socket connects to transition board
•Supplies twenty (16 signal + 4 control) current sources (5mA) to plant contacts and
connects the contact output to digital inputs
•LED indication of current flow.
•Jumpers enable LEDs to be shorted out
•Indication of +24V presence
•Transient voltage protection
2.PRODUCT SPECIFICATIONS
Size: DIN-rail mounted module approx 150x75x45mm
Operating temp: 0 to 45 deg C ambient
Power Requirements: Optional +24V indication of transition board isolated power
Number of channels: 16 signal plus 4 control
Number of signals: I/O 1-16, TRG, CLK, STR, STB, +24V, AGnd, plus 4 spare pairs
Connectors: SCSI 50-way socket for connection to transition board
50-way terminal screws
Transient protection: 26V clamp rising to 40V max @ 10A using varistors
3.BOARD DESCRIPTION
The board is primarily intended to allow plant switch contacts to be sensed using a constant
current. The currents are routed to a VME64X transition card using a 50-way twisted pair SCSI
cable.
The signal pair (source current and signal return) for I/O1 connect between T26 and T1. The
pair for I/O2 connect between T27 and T2 and so on up to T47 and T22. The signals are
connected to the relevant pin numbers on the SCSI connector.
Jumpers J1-J20 can be used to short circuit the respective LEDs when input currents are not
monitored i.e. the LED monitoring is disabled and the circuit is connected straight-through.
The LED which indicates the presence of +24V is over-voltage protected by a varistor.
Links LK1 and LK2 disconnect pins 25 and 50 of the SCSI so that an external PSU can be
connected.
Important Note LK1 and LK2 should not be made as this connects the sup[ply voltages
incorretly. Please contact Hytec for a solution.
4.OPERATION
4.1 Connection to Transition Board
Connect the unit to the SCSI socket on the transition board for the relevant carrier board site
(e.g. lowest of the four connectors for an IP card plugged into site A)
4.2 Select power for current sources
For an external 24V supply open links 1 and 2.and close link 3.
4.3 Connection to Plant Equipment
Connect the signals to the terminals as shown in the table in section 5.
Connect the external supply +24V to terminal 50 and 0V to terminal 25.