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Parameter Areas Section 9-22
Note The CX-Programmer treats condition flags as global symbols beginning with
P_.
The Clock Pulses are read-only; they cannot be overwritten from instructions
or Programming Devices (CX-Programmer or Programming Console).
The Clock Pulses are cleared at the start of operation.
Using the Clock Pulses The following example turns CIO 000000 ON and OFF at 0.5 s intervals.
Clock Pulse Refreshing The clock pulses are refreshed even during program execution. ON/OFF sta-
tus may not be the same at the beginning and end of a program.
Clock Pulse Error The maximum error in the clock pulses is 0.01% (at 25
°C). For long-term,
time-based control, we recommend you use the internal clock instead of the
clock pulses. Be sure to allow for the error in the internal clock.
9-22 Parameter Areas
Unlike the data areas in I/O memory which can be used in instruction oper-
ands, the Parameter Area can be accessed only from a Programming Device.
The Parameter Area is made up of the following parts.
• The PLC Setup
• The Registered I/O Table
• The Routing Table
• The CPU Bus Unit Settings
9-22-1 PLC Setup
The user can customize the basic specifications of the CPU Unit with the set-
tings in the PLC Setup. The PLC Setup contains settings such as the serial
port communications settings and minimum cycle time setting.
Note Refer to the Programming Device’s Operation Manual for details on changing
these settings.
9-22-2 Registered I/O Tables
The Registered I/O Tables are tables in the CPU Unit that contain the informa-
tion on the model and slot location of all of the Units mounted to the CPU
Rack and Expansion Rack. The I/O Tables are written to the CPU Unit with a
Programming Device operation.
The CPU Unit allocates I/O memory to I/O points on Basic I/O Unit and CPU
Bus Units based on the information in the Registered I/O Tables. Refer to the
P_1s
0.5 s
0.5 s
000000
000000
OUT
LD
P_1s
000000
Instruction
Operand
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