User manual

890 USE 145 00
512/612 Modicon Micro PLCs
3
PLC Operating Modes
The PLCs can operate in any one of
three modes:
As a single PLC—i.e., a stand-alone
programmable control system
As a parent PLC on an I/O expan-
sion link—with the ability to access
the fixed I/O resources of the PLC(s)
in child operating mode on the link
As a child PLC whose fixed I/O
resources can be accessed by the
parent on an I/O expansion link
Note Whenever A120 I/O is
used in a child PLC, the logic
that controls the A120 I/O must
be run in the child. A parent
cannot access the A120 I/O con-
nected to a child—it can access
only fixed I/O resources of its
children.
Memory Resources
128 kbytes of RAM
2048 words available for program
memory
2048 words of data memory
110CPU61204 PLC has 8192 words
of user data memory
Note The execution buffer is
large enough to load the XMIT
loadable or the Gas loadable
without reducing the 8K of avail-
able user logic.
Memory Backup Options
User memory—for the system configu-
ration and application program—can be
backed up in three ways:
Using an optional (110XCP98000)
lithium battery assembly
+ --
110XCP98000 Lithium Battery Assembly
Using an optional (110XCP99000)
battery capacitor assembly
110XCP99000 Battery Capacitor Assembly
+
--
Label
Resistor
Capacitor
Writing the information to a reserved
area in the PLC’s Flash RAM
The optional lithium battery or battery
capacitor will automatically back up the
current user memory in the event of a
power shutdown. The battery can
safely back up the data for one year.
The battery capacitor can back up a
typical user logic program for 72 hr.
Note The 110XCP990000 bat-
tery capacitor must be charged in
a powered-up PLC for at least 24
hours to assure full memory back-
up.
The ability to back up user memory by
writing it to Flash RAM is a standard
feature of all Micro PLCs, except the
61204. Because of limitations of Flash
storage capabilities in 61204, a battery
is the only method available to backup
user memory. Memory backed up in
Flash remains completely nonvolatile
over time.