Sensaphone SCADA 3000 Users manual - Manual (Page 158)

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SCADA 3000 User’s Manual
RULeS/CONVeNTIONS OF LADDeR LOGIC PROGRAmmING
1) One output per rung.
2) Each rung controls an output.
3) A normally open contact (XIC Instruction) when evaluated by the program is
examined for a 1 (closed contact) to make the instruction true.
4) A normally closed contact (XIO Instruction) when evaluated by the program is
examined for a 0 (Open contact) to make the instruction true.
5) The output on a given rung will be energized if any left to right path has all con-
tacts closed.
6) An output can control either a connected device (if the UAF is also a termination
point) or an internal output used exclusively within the program.
7) An internal output does not control a field device. It provides interlocking func-
tions within the program.
8) Input contacts can represent input signals sent from connected inputs, contacts
from internal outputs, or contacts from connected outputs.
9) Repeated use of contacts is allowed. A given input, output or internal output can
be used throughout the program as many times as required.
10) Contacts can be programmed in series or parallel depending on the output con-
trol logic required.
11) The maximum number of parallel branches is limited to 6.
12) Only 1 Counter or timer per rung.
13) A RES instruction resets all status bits and the accumulated value for the coun-
ter or timer that is being addressed.
14) Do not use a RES instruction on a TOF instruction.
15) The OSR instruction is not allowed inside a branch.
16) Preset and Accumulated values for timers range from 0 to +32767. If a timer
preset or accumulated value is a negative number, a runtime error will occur.
17) The timer timebase is fixed at 0.01 seconds (10ms).
18) The preset and accumulated values for counters range from -32768 to +32767,
and are stored as signed integers. Negative values are stored in 2’s complement
form.
19) When using an RES instruction to reset an alarm, an OSR instruction should
be used preceding the RES to prevent continuous alarm resetting.
DeSCRIPTION OF LADDeR eLemeNTS AND FUNCTIONS
Each ladder logic symbol or functional block will contain an address field, a title field and a
comment field. Timers and counters will contain additional fields for preset’s and accumulated
values. Listed below is the logic definition for the SCADA 3000.
Logic Definition
Contact State Bit Value Input Voltage
Open 0 (Off) 5V
Closed 1 (On) 0V