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If IR 00000 in the above diagram is OFF (i.e., if the execution condition for the
first INTERLOCK instruction is OFF), instructions 1 through 4 would be
executed with OFF execution conditions and execution would move to the
instruction following the INTERLOCK CLEAR instruction. If IR 00000 is ON, the
status of IR 00001 would be loaded as the execution condition for instruction 1
and then the status of IR 00002 would be loaded to form the execution condition
for the second INTERLOCK instruction. If IR 00002 is OFF, instructions 2
through 4 will be executed with OFF execution conditions. If IR 00002 is ON, IR
00003, IR 00005, and IR 00006 will determine the first execution condition in
new instruction lines.
4-7-8 Jumps
A specific section of a program can be skipped according to a designated execu-
tion condition. Although this is similar to what happens when the execution
condition for an INTERLOCK instruction is OFF, with jumps, the operands for all
instructions maintain status. Jumps can therefore be used to control devices
that require a sustained output, e.g., pneumatics and hydraulics, whereas inter-
locks can be used to control devices that do not required a sustained output,
e.g., electronic instruments.
Jumps are created using the JUMP (JMP(04)) and JUMP END (JME(05))
instructions. If the execution condition for a JUMP instruction is ON, the program
is executed normally as if the jump did not exist. If the execution condition for the
JUMP instruction is OFF, program execution moves immediately to a JUMP
END instruction without changing the status of anything between the JUMP and
JUMP END instruction.
All JUMP and JUMP END instructions are assigned jump numbers ranging
between 00 and 99. There are two types of jumps. The jump number used deter-
mines the type of jump.
A jump can be defined using jump numbers 01 through 99 only once, i.e., each of
these numbers can be used once in a JUMP instruction and once in a JUMP
END instruction. When a JUMP instruction assigned one of these numbers is
executed, execution moves immediately to the JUMP END instruction that has
the same number as if all of the instruction between them did not exist. Diagram
B from the TR bit and interlock example could be redrawn as shown below using
a jump. Although 01 has been used as the jump number, any number between
01 and 99 could be used as long as it has not already been used in a different part
of the program. JUMP and JUMP END require no other operand and JUMP END
never has conditions on the instruction line leading to it.
Instruction 1
00002
00000
Instruction 2
Diagram B: Corrected with a Jump
00001
JME(05) 01
JMP(04) 01
Address Instruction Operands
00000 LD 00000
00001 JMP(04) 01
00002 LD 00001
00003 Instruction 1
00004 LD 00002
00005 Instruction 2
00006 JME(05) 015
This version of diagram B would have a shorter execution time when 00000 was
OFF than any of the other versions.
Inputting, Modifying, and Checking the Program Section 4-7