Siemens 505-2557 Centigrade or, Degrees Fahrenheit, Alarm Setpoints

Additional Information about Each Function (continued)

Degrees	In advanced mode the selection of degrees C or F is controlled by the
Centigrade or	information stored and transferred to the module at WY72. The default
Degrees Fahrenheit	parameters are all zeroes which will cause the SIMATIC 505±2557 module
	to return the value in degrees Centigrade x10. To select degrees F for the
	module write a value of FFFF Hex to WY72 and use the documented
	transfer procedure setting the data identification bits Y17, Y18 and Y19 to
	1, 0, 0, (Refer to section 3.7).
	To verify the Fahrenheit/Centigrade settings, the module reports back its
	F/C status in WX57. The least significant bit (LSB) of WX57, corresponds to
	channel one, while the most significant bit (MSB) corresponds to channel
	16. A status bit of ª1º indicates the channel is reporting in degrees F.
	A status bit of ª0º indicates the channel is reporting in degrees C.
Scaling	Numerical Range All numbers used for scaling are expressed as signed
	integers.
	The numerical range for scaling is ± 32767. If a value of ±32768 is loaded
	into the module, then the value will be adjusted in the module to ±32767.
	Arithmetic Overflow Scaling operations may result in arithmetic
	overflow. Errors of this kind for each channel may be detected with the
	WX54 arithmetic overflow bits.
	Overflow conditions can occur during normalization of the input value. If
	the input word reaches + 32767 or ±32767 before the ADC (analog-to-digital
	converter) saturates, then an overrange condition occurs and the overrange
	bit for that channel is set.
	In a scaling operation, if the result of scaling forces the value to the PLC to
	exceed 32767, the overrange bit for that channel is set.
	During an overflow condition, the value to the controller defaults to ± 32767
	and there is no rollover of data. That is, the data does not return to zero and
	beyond.
Alarm Setpoints	Numerical Range All numbers used for alarm setpoints are expressed as
	signed integers. The numerical range for scaling is ±32767. If a value of
	±32768 is loaded into the module, then the value in the module is adjusted
	to ±32767.

3-20 Advanced Function Programming SIMATIC 505±2557 Installation and Operation Guide