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How to Use the Step Ladder Program Block Appendix A
List of Sequence Control Instructions
Internal Switch Block
• To receive data internally by the Step Ladder Program without outputting it to the block address and ITEM
number, specify the Internal Switch block (Block Model 209) as the block address.
Command Ladder
symbol
Operand Description Input
conditions
°:Can be used
−×:Cannot be used
In logic
sequence
In step
sequence
STEP Step num-
ber
STEP declares the step number, and has no
input conditions (is a direction connection to the
bus).
Any numbers in the range 00 to 99 are used as
the step number, and are placed in ascending
order.
1)Logic sequence: The step number is fixed at
00, and is functional at all times. Declaration of
step number 00 can be omitted.
2)Step sequence: When the step number is
within the range 01 to 99, only one of the steps is
functional. When the program is started, step
number 01 is functional.
Not required ° °
BLOCK SET Block
address/
step num-
ber
When the input conditions turn ON, operation of
the specified step number of the Step Ladder
Program block at the specified block address
(701 to 900) is started.
Run/stop command S1 of the specified block
turns automatically 1 (ON). Operation of currently
executing steps in already operating Step Ladder
Program blocks is interrupted, and execution of
the program jumps to the specified step.
Required --- °
BLOCK
RSET
Block
address
When the input conditions turn ON, operation of
the Step Ladder Program block is stopped at the
specified block address (701 to 900).
Run/stop command S1 of the specified block
automatically turns 0 (OFF).
Required ×− °
JUMP Block
address/
step num-
ber
When the input conditions turn ON, execution of
the program jumps to the specified step number
(01 to 99) of the Step Ladder Program block at
the specified block address (701 to 900).
• To specify a jump to the current step number,
set the block address to 000.
• When a jump is made to another Step Ladder
Program block, run/stop command S1 of the
source block automatically turns 0 (OFF), and
run/stop command S1 of the destination block
turns 1 (ON).
Required ×−× °
STEP TIMER Timer set-
ting value
This is the timer (setting range: 0 to 9999 s) for
moving between steps. It has no input conditions.
(STEP TIMER is placed in the same line as the
STEP command.)
Operation is started when program execution
moves to the line containing the STEP command.
When the time set by STEP TIMER is reached,
the program execution moves to the next step.
Note: “Input condition commands” are given top
priority.
Not required ×−× °
ALARM
TIMER
Timer set-
ting value
This is the timer (setting range: 0 to 9999 s) for
monitoring steps. It has no input conditions.
(ALARM TIMER is placed in the same line as the
STEP command.)
Operation is started when program execution
moves to the line containing the STEP command.
When the time set by ALARM TIMER is reached,
the Step Timer Completion flag (step congestion
indicator) turns 1 (ON).
At this time, the step is held at the current values.
Not required ×−× °
STEP
Step number
BS
BR
JUMP
STEP TIMER
ALM TIMER
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