Rockwell Automation 1785-Vx0B, D17856.5.9 PLC-5 VME VMEbus Programmable Controllers User Manual - Manual (Page 28)

Chapter 2
Installation
2-6
The specific procedure for grounding a VME chassis varies depending on
the style of the chassis. Read the instructions found in the Classic PLC-5
Family Programmable Controllers Installation Manual, publication
1785-6.6.1 for information on how Allen-Bradley racks are grounded, and
try to ground your VME chassis frame in a similar way.
ATTENTION: If you are using a PLC-5/V40L processor,
your VME power supply should not float with respect to earth
ground. Connect the power supply’s logic ground (common)
for the 5V supply before connecting the PLC-5/40L processor
to a 1771-ALX adapter. Also, use a single point of ground
between the VME chassis and the extended-local I/O system to
ensure proper performance.
The PLC-5/VME processor draws 4 A (maximum)—3.2 A (typical)—from
the VME power supply. The processor also monitors the ACFAIL signal
on the backplane to determine when the +5 VDC supply is within
tolerances. The VME power supply must assert ACFAIL at least 9 ms in
advance of the +5 VDC supply dropping beneath 4.75V or memory
corruption and processor fault occurs. Therefore, make sure that your
power supply has ACFAIL capability.
You must use a Safety Extra Low Voltage (SELV)- or Protected Extra Low
Voltage (PELV)-certified power supply with the VME processor to comply
with Low Voltage directive requirements.
Use Belden 9463 twin-axial cable (cat. no.1770-CD) to connect devices to
a remote I/O link. To connect a remote I/O link, do the following:
To connect a remote I/O link, you must: See page:
Make sure the cables are the correct length 2-6
Prepare the cable 2-7
Make the remote I/O connections 2-7
Terminate the link 2-8
Make Sure that You Have Correct Cable Lengths
Verify that your system’s design plans specify remote I/O cable lengths
within allowable measurements.
Determining Power-Supply
Requirements
Connecting to Remote I/O