Implementation-dependent parameters

IEC compliance table for implementation-dependent parameters:

Parameters	Limitations/Behavior
Maximum length of identifiers	32 characters
Maximum comment length	Within the Control Expert: 1024 characters for each editor object. Import: limited by XML constraints or UDBString usage in the persistent layer.
Syntax and semantics of pragmas	Unity Pro V1.0 only implements 1 pragma, used for legacy convertor: `{ ConvError (' error text'); }` any other pragma construct is ignored (a warning message is given) NOTE: Unity Pro is the former name of Control Expert for version 13.1 or earlier.
Syntax and semantics for the use of the double-quote character when a particular implementation supports Feature #4 but not Feature #2 of Table 5.	(#2 of table 5 is supported)
Range of values and precision of representation for variables of type `TIME`, `DATE`, `TIME_OF_DAY` and `DATE_AND_TIME`	for `TIME` : `t#0ms .. t#4294967295ms` (=t`#49D_17H_2M_47S_295MS`) for `DATE`: `D#1990-01-01 .. D#2099-12-31` for `TOD`: `TOD#00:00:00 .. TOD#23:59:59`
Precision of representation of seconds in types `TIME`, `TIME_OF_DAY` and `DATE_AND_TIME`	`TIME`: precision 1 ms `TIME_OF_DAY`: precision 1 s
Maximum number of enumerated values	Not applicable
Maximum number of array subscripts	6
Maximum array size	64 kbytes
Maximum number of structure elements	no limit
Maximum structure size	no limit
Maximum range of subscript values	`DINT` range
Maximum number of levels of nested structures	10
Default maximum length of `STRING` and `WSTRING` variables	16 characters
Maximum allowed length of `STRING` and `WSTRING` variables	64 kbytes
Maximum number of hierarchical levels Logical or physical mapping	Premium: physical mapping (5 levels) Quantum: logical mapping (1 level)
Maximum number of inputs of extensible functions	The number of all input parameters (including in-out parameters) is limited to 32. The number of all output parameters (including in-out parameters) is also limited to 32. Thus the limit for extensible input parameters is (32 - number of input parameters - number of in-out parameters). The limit for extensible output parameters is (32 - number of output parameters - number of in-out parameters).
Effects of type conversions on accuracy	See online help.
Error conditions during type conversions	Error conditions are described in the online-help. Globally `%S18` is set for overflow errors detected. `ENO` is also set. The result is depending on the specific function.
Accuracy of numerical functions	INTEL floating point processing or emulation.
Effects of type conversions between time data types and other data types not defined in Table 30	See online help.
Maximum number of function block specifications and instantiations	Only limited by the maximum size of a section.
Function block input variable assignment when `EN` is `FALSE`	No assignment
`Pvmin`, `Pvmax` of counters	`INT` base counters: `Pvmin`=-32768 (0x8000) `Pvmax`=32767 (0x7FFF) `UINT` base counters: `Pvmin`=0 (0x0) `Pvmax`=65535 (0xFFFF) `DINT` base counters: `Pvmin`= -2147483648 (0x80000000) `Pvmax`=2147483647 (0x7FFFFFFF) `UDINT` base counters: `Pvmin`=0 (0x0) `Pvmax`=4294967295 (0xFFFFFFFF)
Effect of a change in the value of a `PT` input during a timing operation	The new `PT` values are immediately taken at once into account, even during a running timing operation immediately works with the new values.
Program size limitations	Depends on controller type and memory
Precision of step elapsed time	10 ms
Maximum number of steps per SFC	1024 steps per SFC section
Maximum number of transitions per SFC and per step	Limited by the available area for entering steps/transitions and by the maximum number of steps per SFC section (1024 Steps). 32 transition per step. Limited by the available area for entering Alternative/Parallel branches, maximum is 32 rows.
Maximum number of action blocks per step	20
Access to the functional equivalent of the `Q` or `A` outputs	not applicable
Transition clearing time	Target dependent; always < 100 micro-seconds
Maximum width of diverge/converge constructs	32
Contents of `RESOURCE` libraries	Not applicable
Effect of using `READ_WRITE` access to function block outputs	Not applicable
Maximum number of tasks	Depends on controller type. Maximum on most powerful controller: 9 tasks
Task interval resolution	10 ms
Maximum length of expressions	Practically no limit
Maximum length of statements	Practically no limit
Maximum number of `CASE` selections	Practically no limit
Value of control variable upon termination of `FOR` loop	Undefined
Restrictions on network topology	No restrictions
Evaluation order of feedback loops	The block connected to the feedback variable is executed first