ao Records

Normal Operation

Depending on the format type, different record fields are used for output and input. The variable x stands for the written or read value.

DOUBLE format (e.g. %f):

Output: x=(OVAL-AOFF)/ASLO
Input: VAL=x*ASLO+AOFF
In both cases, if ASLO==0.0, it is treated as 1.0. Default values are ASLO=1.0, AOFF=0.0.
Note that OVAL is not necessarily equal to VAL if OROC!=0.0.

LONG format (e.g. %i):

Output: x=RVAL
Input: RBV=RVAL=x
Note that the record calculates RVAL=(((OVAL-EOFF)/ESLO)-AOFF)/ASLO if LINR=="LINEAR". ESLO and EOFF might be set in the record definition. StreamDevice does not set it. For example, EOFF=-10 and ESLO=0.000305180437934 (=20.0/0xFFFF) maps -10.0 to 0x0000, 0.0 to 0x7FFF and 10.0 to 0xFFFF. Using unsigned formats with values ≥ 0x800000 gives different results on 64 bit machines.

If LINR=="NO CONVERSION" (the default), OVAL is directly converted to long without going through RVAL. This allows for more bits on 64 bit machines. To get the old behavior, use LINR=="LINEAR".

ENUM format (e.g. %{):

Not allowed.

STRING format (e.g. %s):

Not allowed.

Initialization

During initialization, the @init handler is executed, if present. In contrast to normal operation, output in DOUBLE format uses VAL instead of OVAL. Note that the record initializes VAL from DOL if that is a constant.