Omron E5AF, Operation Manual

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4--2 Setting Before Power Application
Make all the proper switch settings as described in
3--2 Before Applying Pow-
er
before applying power to the E5AF. However, no terminator designation is
necessary.
4--3 Operations: Front Key Section
There is no need to set a baud rate or other communications parameters with
the operating keys of E5AF-
=
20 (BCD) Controllers. For additional information
about the operation, refer to the operating procedures in the datasheet.
4--4 Communications Programming
4--4--1 Things to Remember
1, 2, 3... 1. Process values and set values must be read and written in units of four
digits. If all four digits are not written/read, no data will be written or the
E5AF will continue displaying the previous data even after reading
starts.
2. The read data is renewed in the following situations:
•
On the falling edge of the VAL signal.
•
When a new data select code is set.
•
After the four digits of the present data is read, but before reading the next
set of data.
3. Data can be received when the VAL signal is low.
4. Data is read after the rising edge of the BUSY signal.
5. When writing, set the write data and then change the select code.
6. The select code is read on the falling edge of the BUSY signal. Do not
change the select code while the BUSY signal is high.
7. Once the select code has been changed, do not change it again until
after the falling edge of the next BUSY signal.
8. If the VAL signal goes high while the BUSY signal is low (under pro-
cess), select code processing may be interrupted. Do not change the
VAL signal while the BUSY signal is high.
9. Wait at least 20 ms after the BUSY signal has gone high (OFF) before
changing the VAL signal. VAL signal detection requires a maximum of
20 ms.
10. For negative values, write F as the leftmost digit (e.g. --23
A
C = F023).
11. When several Controllers have been connected into a wired-OR data
line, keep each VAL signal high for at least 20 ms.
4--4--2 Communications Errors
When an error occurs, it will not be displayed, but the BUSY signal will be
output. A communications error will occur under the following conditions:
•
When an undefined select code is sent.
•
When improper four-digit writing data has been set.
•
When read or write data cannot be set (refer to the note below).
•
When a write command is received while the Controller is in local mode or
is auto-tuning.
Note The Alarm Temperature (2) (AL2) for E5AF-AH
=
cannot be set.
Section 4--4