Exchanging Data with the CPU Unit
Section
3-3
116
3-3-1-2
Run status of Loop Control Unit
The run status of the Loop Control Unit is reflected at all times in bits 00 to 05
of the leading word n of the allocated CIO area (25 words per Unit within the
range 1500 to 1899 words are occupied according to the unit number) on the
CPU Bus Unit. For this reason, the required processing can be executed by
the Step Ladder Program of the CPU Unit taking this run status as the input
conditions.
Loop Control Unit
CPU Unit
Allocated CIO Area
Note
On the Loop Control Unit, the refresh timing of the allocated relay n words for
the CPU Bus Unit is not the I/O refresh timing of the CPU Unit, but the
refresh timing of the 1 sec operation cycle (fixed).
Allocated CIO area nth Word on CPU Bus Unit
n = 1500 + unit number x 25
Bit
1 (ON)
0 (OFF)
Explanation
00
Loop Control Unit
running
Loop Control Unit
stopped
This bit informs the CPU Unit whether or not the Loop Control
Unit is running.
01
PV error input ON
PV error input OFF
This bit informs the CPU Unit whether ITEM018 (PV error input)
of the Basic PID block (Block Model 011) or the Advanced PID
block (Block Model 012) is ON or OFF.
Basically, ITEM018 (PV error input) specifies the output from
disconnected line detection contact ITEM of the Analog Input
Unit as the source designation.
02
MV error input ON
MV error input OFF
This bit informs the CPU Unit whether ITEM090 (MV error input)
of the Basic PID block (Block Model 011) or the Advanced PID
block (Block Model 012) is ON or OFF.
Basically, ITEM090 (MV error input) specifies the output from
disconnected line detection contact ITEM of the Analog Output
Unit as the source designation.
03
Execution error
(error code other
than 0)
No execution error
(error code 0)
This bit informs the CPU Unit that execution of the function block
ended in error when ITEM003 (execution error indication) of one
or more of the function blocks is other than 0 (normal).
For details of execution errors (error codes other than 0) and
how to remedy execution errors, see 7-1 Errors and Alarm
Troubleshooting.
04
Function block
database error
No function block
database error
This bit informs the CPU Unit that the function block data in RAM
on the Loop Control Unit has been corrupted by a low battery
voltage, for example.
For details of LED lighting at this time, see 7-1 Errors and Alarm
Troubleshooting.
When this error occurs, either initialize RAM using CX-Process
Tool, or re-set the function block in question.
05
Battery error
No battery error
This bit informs the CPU Unit whether the battery voltage has
fallen or the battery is not inserted when pin 2 of the DIP switch
is OFF. Check the battery connection. Replace the battery if the
connection is normal.
For details on how to replace the battery, see 7-2 Maintenance.
15
Function block
changed
(Download by
function block)
(See note.)
No function block
changed (Not
downloaded by
function block or
hot or cold start)
Notifies the CPU Unit when a function block has been
downloaded from the CX-Process Tool while the Loop Control
Unit is running. Monitor this bit from the ladder program in the
CPU Unit to detect changes to function blocks and perform
suitable processing (e.g., notification).