User manual

512/612 Modicon Micro PLCs
52
890 USE 145 00
A120 I/O Expansion
On the right side of the PLC is a 30-pin
connector that allows you to connect
the unit to a secondary backplane (or
rack) containing A120 I/O modules.
This expansion capability can support
up to 15 A120 I/O modules (depending
on the modules’ combined power draw)
in up to three DTA racks.
A 512/612 PLC in any operating
mode—single, parent, or child—can use
A120 I/O expansion. If a PLC using the
A120 I/O is a child PLC on an I/O ex-
pansion link, the A120 I/O can be ac-
cessed only by that child, not by the
parent on that expansion link.
A120 I/O
tie point
Calculating Power Requirements in an A120 I/O Expansion
System
The PLC has a 250 mA internal power
supply for A120 I/O expansion. When
planning an expansion system, you
must be aware of the power require-
ments of the A120 modules you want to
use.
To calculate these A120 power require-
ments, add up the maximum internal
power draw specified for each module
in your expansion system. Internal
power specifications can be found in
A120 Series I/O Modules User Guide
890USE10900 formerly (GM-A984-IOS).
Caution All internal power
requirements for the A120
modules must be satisfied by
the Modicon Micro PLC. A
total internal power supply of
250 mA is available from the
PLC for all modules in all
racks.
A120 modules such as the BDEP 216
DC input module and the BDAP 208 DC
output module, which draw 15 mA each,
enable you to power three fully loaded
DTA 201 expansion racks.
However, in applications that use A120
modules with large internal power
draws—e.g., the BDEP 218 AC input
module or the BDAP 210 AC output