Siemens SIMATIC S5 Manual page 93

Data Exchange with the Central Controller
Byte 0/1 Temperature setpoint
If the value 0 C or
takes place and only the actual value is indicated. A check is made to establish
whether the entered setpoint is between 0 and a maximum value dependent on
the connected thermocouple.
The setpoints of the special function are described in Section 3.4. The maximum
values listed above are valid for the linearization of the characteristic curve stored
in the firmware. If the linearization of the characteristic curve is disabled
( bit 3 in control byte 2 set to 1) and if a normalization value is specified in
messages 30 to 42, the maximum selectable temperature setpoint can be
calculated as shown below.
If the maximum value is exceeded, an error identifier is set (bit 4 in the
corresponding error byte) and the setpoint is limited to the maximum value.
Byte 2 1st positive tolerance
If the actual temperature is above the setpoint plus the first positive tolerance, an
error identifier is set (bit 0 in the appropriate error byte). If the value 0 is entered,
the tolerance is not effective.
Byte 3 1st negative tolerance
If the actual temperature is below the setpoint minus the first negative tolerance,
an error identifier is set (bit 1 in the appropriate error byte). If the value 0 is entered,
the tolerance is not effective.
Byte 4/5 Lower setpoint
If bit 5 is set in main control byte 4, the lower setpoint is used as the setpoint
provided it is lower than the temperature setpoint. The plausibility check is
performed as for the temperature setpoint.
4–26
32 F (if specified in Fahrenheit) is entered, no control
IP244
C79000–B8576–C860–02