49
4-3-4 Operation Timing
Write Operation Timing
ON
OFF
ON
OFF
Approx.
140 ms
Command (Wd n)
Write data (Wd n+1)
Write request
(Wd n+2), bit 00
Data (1)
Data (2)
Data (3)
Data (4)
Write complete
(Wd n+6), bit 08
1, 2, 3...
1. The data is written to the PID Control Unit EEPROM when the Write Request
Flag turns ON.
2. The Write Complete Flag turns ON when the data writing operation is com-
pleted. It takes approximately 140 ms to write the data.
3. The Write Complete Flag automatically turns OFF when the Write Request
Flag turns OFF.
Check to be sure that the Write Complete Flag has turned ON before turning
OFF the Write Request Flag. If the Write Request Flag is set to OFF before
the Write Complete Flag turns ON, the write operation will not be successful.
Temporarily turn the Write Request Flag OFF before executing the second
and subsequent write operations. Writing is enabled on the ON rising edge
of the Write Request Flag.
The Loop 1 and 2 executed bank number (Wd n+2) sets data directly. The
data is written to the PID Control Unit RAM. If the value is set out of this
range, the bank number reverts to the previous value (default value = 1).
Timing for a Read Operation
ON
OFF
Approx.
140 ms
Command (n)
Command (A)
Command (B)
Read complete
(Wd n+6),
bit 00
Read data
(Wd n+5)
Read data (A)
Read data (B)
1, 2, 3...
1. The read data is output to Wd (n+5) approximately 140 ms after the Read
command is executed.
2. The read data is updated every 100 ms.
3. When the Read command is modified, turn OFF the Read Complete Flag to
execute the next read operation.
PID control will not be executed properly unless there are at least 20 ms be-
tween I/O refresh operations. When creating the program, be sure that all of
the conditions descried below are satisfied.
•
The cycle time must be a minimum of 20 ms. If the program processing time is
short, it is recommended that the fixed cycle time instruction (SCAN18) be
used.
•
When IORF(97) is executed for the PID Control Unit, there must be an interval
of at least 20 ms between prior and subsequent end refreshes.
I/O Refresh
Programming
