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Example

In the example, whenever input %I0001 is set, bit 12 of the string beginning at reference
%R0040 is set to 1.

Figure 253

23.1.9

Bit Operation Functions
Masked Compare

The Masked Compare function compares the contents of two separate bit strings. It
provides the ability to mask selected bits. Input string 1 might contain the states of outputs
such as solenoids or motor starters. Input string 2 might contain their input state feedback,
such as limit switches or contacts.

Figure 254

When the function receives power flow, it begins comparing the bits in the first string with
the corresponding bits in the second string. Comparison continues until a miss-compare is
found or until the end of the string is reached.

The BIT input stores the bit number where the next comparison should start (a 0 indicates
the first bit in the string). The BN output stores the bit number where the last comparison
occurred (where a 1 indicates the first bit in the string). Using the same reference for BIT
and BN causes the compare to start at the next bit position after a miss-compare; or, if all
bits compared successfully upon the next invocation of the function block, the compare
starts at the beginning.

To start the next comparison at some other location in the string, you can enter different
references for BIT and BN. If the value of BIT is a location that is beyond the end of the string,
BIT is reset to 0 before starting the next comparison.

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Parameters of the Masked Compare Function

Input/
Output

Choices

Description

enable

flow

Permissive logic to enable the function.

IN1

R, AI, AQ
For WORD only: I, Q, M, T, S, G

Reference for the first bit string to be compared.

IN2

R, AI, AQ
For WORD only: I, Q, M, T, S, G

Reference for the second bit string to be compared.

R, AI, AQ
For WORD only: I, Q, M, T, SS,
SB, SC, G

Reference for the bit string mask.

BIT

I, Q, M, T, S, G, R, AI, AQ,
constant

Reference for the bit number where the next
comparison should start.

flow, none

User logic to determine if a miscompare has occurred.

R, AI, AQ
For WORD only: I, Q, M, T, SA,
SB, SC, G

Output copy of the mask (M) bit string.

I, Q, M, T, S, G, R, AI, AQ

Bit number where the last miscompare occurred.

length

Constant

The number of words in the bit string. Max. is 4095 for
WORD and 2047 for DWORD.

Operation of the Masked Compare

all corresponding bits in strings IN1 and IN2 match, the function sets the “miss

compare”

output MC to 0 and BN to the highest bit number in the input strings.  The comparison then
stops.  On the next invocation of a Masked Compare Word, it is reset to 0. When the two bits
currently  being  compared  are  not  the  same,  the  function  checks  the  correspondingly
numbered bit in string M (the mask).  If the mask bit is a 1, the comparison continues until
it  reaches  another  miss-compare  or  the  end  of  the  input  strings.  If  a  miss-compare  is
detected and the corresponding mask bit is a 0, the function does the following:

Sets the corresponding mask bit in M to 1.

Sets the miss-compare (MC) output to 1.

Updates the output bit string Q to match the new content of mask string M

Sets the bit number output (BN) to the number of the miss-compared bit.

Stops the comparison.

Example

In the example, after first scan the Masked Compare Word function executes. It compares
%M0001

–

16 with %M0017

–

32. %M0033

–

48 contains the mask. The value in %R0001

determines the bit position in the two input strings where the comparison starts.

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Figure 255

Before the function block is executed, the contents of the above references are:

Figure 256

The contents of these references after the function block executes are:

Figure 257

In this example, contact %T1 and coil %M100 force one and only one execution; otherwise
the function would repeat with possibly unexpected results.

23.1.10

Bit Operation Functions
Bit Position

The Bit Position function locates a bit set to 1 in a bit string.

Each sweep that power is received, the function scans the bit string starting at IN. When
the function stops scanning, either a bit equal to 1 has been found or the entire length of
the string has been scanned.

POS is set to the position within the bit string of the first non-zero bit; POS is set to zero if
no non-zero bit is found.

A string length of 1 to 256 words can be selected. The function passes power flow to the
right whenever enable is ON.

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Figure 258

Parameters for the Bit Position Function

Input/
Output

Choices

Description

enable

flow

When the function is enabled, a bit search operation is
performed.

I, Q, M, T, S, G, R, AI, AQ

IN contains the first word of the data to be operated on.

flow, none

The OK output is energized whenever enable is energized.

POS

I, Q, M, T, G, R, AI, AQ

The position of the first non-zero bit found, or zero if a
non-zero bit is not found.

Example

In the example, if %I0001 is set, the bit string starting at %M0001 is searched until a bit equal
to 1 is found. Coil %Q0001 is turned on. If a bit equal to 1 is found, its location within the bit
string is written to %AQ001. If %I0001 is set, bit %M0001 is 0, and bit %M0002 is 1, then the
value written to %AQ001 is 2

Figure 259

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23.1.11

Bit Operation Functions
Bit Sequencer

The Bit Sequencer function performs a bit sequence shift through an array of bits.

Figure 260

The operation of the function depends on the previous value of the parameter EN:

R Current
Execution

EN Previous
Execution

EN Current
Execution

Bit Sequencer Execution

OFF

Bit sequencer does not execute.

OFF

Bit sequencer increments/decrements
by 1.

OFF

Bit sequencer does not execute.

OFF

Bit sequencer does not execute.

ON/OFF

Bit sequencer resets.

The reset input (R) overrides the enable (EN) and always resets the sequencer. When R is
active, the current step number is set to the value passed in via the step number parameter.
If no step number is passed in, step is set to 1.  All of the bits in the sequencer are set to 0,
except for the bit pointed to by the current step, which is set to 1.

When Enable is active and Reset is not active, the bit pointed to by the current step number
is cleared. The current step number is incremented or decremented, based on the direction
parameter. Then, the bit pointed to by the new step number is set to 1.

The  parameter  ST  is  optional.    If  it  is  not  used,  the  Bit  Sequencer  function  operates  as
described above, except that no bits are set or cleared.  The function just cycles the current
step number through its legal range.

Memory Required for a Bit Sequencer

Each bit sequencer uses three words (registers) of %R memory to store the information:

word 1

current step number

word 2

length of sequence (in bits)

word 3

control word

Word 3 (the control word) stores the state of the Boolean inputs and outputs of its
associated function block, in the following format:

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Figure 261

Parameters for the Bit Sequencer Function

Input/
Output

Choices

Description

address R

Address is the location of the bit sequencer’s current step,

length, and the last enable and OK status.

enable

flow

When the function is enabled, if it was not enabled on the
previous sweep and if R is not energized, the bit sequence
shift is performed.

flow

When R is energized, the bit sequencer’s step number is set

to the value in STEP (default = 1), and the bit sequencer is
filled with zeros, except for the current step number bit.

DIR

flow

When DIR is energized, the bit sequencer’s step number is

incremented prior to the shift. Otherwise, it is
decremented.

STEP

I, Q, M, T, G, R, AI, AQ,
constant, none

When R is energized, the step number is set to this value.

I, Q, M, T, SA, SB, SC, G, R,
AI, AQ, none

ST contains the first word of the bit sequencer. Optional.

flow, none

The OK output is energized whenever the function is
enabled.

Example

In the example, the Bit Sequencer operates on register memory %R0001. Its static data is
stored in registers %R0010

–

12. When CLEAR is active, the sequencer is reset and the current

step is set to step number 3. The first 8 bits of %R0001 are set to zero.

When NXT_CYC is active and CLEAR is not active, the bit for step number 3 is cleared and
the bit for step number 2 or 4 (depending on whether DIR is energized) is set.

Figure 262

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23.2

Control Functions

This section describes the control functions, which may be used to limit program execution
and to change the way the CPU executes the application program.

•

Service specified I/O: DO IO

•

Go to a subroutine block: CALL

•

Temporary program end: END

•

Execute a group of logic rungs without power flow: MCR

•

Go to a specified location in the program: JUMP, LABEL

•

Place a text explanation in the program logic: COMMENT

•

Provide predefined On/Off patterns to a set of 16 discrete outputs in the manner of
a mechanical DRUM SEQUENCER.

The more complex Control Functions; Service Request and the PID algorithms, are
described in other chapters of this manual.

23.2.1

Control Functions
Do I/O

The Do I/O function updates inputs or outputs for one scan while the program is running.
The Do I/O function can also be used to update selected I/O during the program in addition
to the normal I/O scan.

Figure 263

Execution of the function continues until all inputs in the selected range have reported or all
outputs have been serviced. Program execution then returns to the next function.

The function passes power to the right whenever power is received, unless:

•

Not all references of the type specified are present within the selected range.

•

The Micro PLC is not able to properly handle the temporary list of I/O created by the
function.

•

The range specified includes modules associated with a “Loss of I/O" fault.

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Using DO I/O with Expansion Units

The  Do  I/O  function  always  correctly  updates  the  reference  addresses  of  the  I/O  being
scanned, even if some I/O addresses have been skipped in auto-configuring the PLC. If a 14-
point  Micro  PLC  with  attached  expansion  I/O  is  auto-configured,  I/O  addresses  I0009
through I0016 and  Q0009 through Q0016 are skipped  and the I/O addresses of the first
expansion  unit  will  start  at  I0017  and  Q0017.  The  Do  I/O  function  updates  these  I/O
correctly, without reserving the skipped memory areas. The reference memory at the Do
I/O ALT parameter contains 16 points of data: 8 points for the module and 8 points for the
expansion unit.

Note:

Using DO_IO with the ALT parameter to expansion modules IC200UDD06, UEC208, UEI016,
UEO008, and UER016 is not supported.

Parameters of the Do I/O Function

Input/
Output

Choices

Description

enable

flow

When the function is enabled, a limited input or output scan is
performed.

I, Q, AI, AQ

The starting address of the I/O to be serviced.

END

I, Q, AI, AQ

The ending address of the I/O to be serviced.

ALT

I, Q, M, T, G, R,
AI, AQ, none

For the input scan, ALT specifies the address to store scanned input
point/word values. For the output scan, ALT specifies the address to
get output point/word values from. If a constant value is specified for
ALT, it is ignored.

flow, none

OK is energized when the scan completes normally.

Do I/O for Inputs

If input references are specified, when the function receives power flow, the PLC scans input
points from the starting reference (ST) to the END reference.  If a reference is specified for
ALT, copies of the new input values are placed in memory beginning at that reference, and
the real input values are  not updated.  ALT must be the same  size as the reference type
scanned.  If a discrete reference is used for ST and END, ALT must also be discrete.

If no reference is specified for ALT, the real input values are updated. This allows inputs to
be scanned one or more times during the program execution portion of the CPU sweep.

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Example Do I/O for Inputs:

In this example, when the function receives power flow, the PLC scans references %I0001-
64 and %Q0001 is turned on. Copies of the scanned inputs are placed in internal memory
from %M0001-64. Because a reference is specified for ALT, the real inputs are not updated.
This allows the current values of inputs to be compared with their values at the beginning of
the scan.

Figure 264

Do I/O for Outputs

If output references are specified, when the function receives power flow, the PLC writes the
latest output values from the starting reference (ST) to the END reference to the output
points. If outputs should be written to the output points from internal memory other than
%Q or %AQ, the beginning reference can be specified for ALT.

Example Do I/O For Outputs:

In the next example, when the function receives power flow, the PLC writes values from
references %R0001-0004 to analog output channels %AQ001-004 and %Q0001 is turned on.
Because a reference is entered for ALT, the values at %AQ001-004 are not written to.

Figure 265

If no reference were specified for ALT, the PLC would write values at references %AQ001-
004 to analog output channels.

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23.2.2

Control Functions
Call

The Call function causes program execution to go to a specified subroutine block.

Figure 266

When the Call function receives power flow, it causes the scan to go immediately to the
designated subroutine block and execute it. After the subroutine block execution is
complete, control returns to the point in the logic immediately following the Call
instruction.

Example

Figure 267

23.2.3

Control Functions
End of Logic

The End of Logic function provides a temporary end of logic. The program executes from
the first rung to the last rung or the End of Logic function, whichever is encountered first.

The End of Logic function unconditionally terminates program execution. There can be
nothing after the end function in the rung. No logic beyond the End of Logic function is
executed, and control is transferred to the beginning of the program for the next sweep.

The End of Logic function is useful for debugging purposes because it prevents any logic
which follows from being executed.

The programming software provides an [ END OF PROGRAM LOGIC ] marker to indicate the
end of program execution. This marker is used if no End of Logic function is programmed in
the logic.

Figure 268

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Example

In the example, an End of Logic function is programmed to terminate the end of the current
sweep.

Figure 269

23.2.4

Control Functions
Master Control Relay (MCR) / End MCR

All rungs between an active Master Control Relay (MCRN) and its corresponding End Master
Control  Relay  (ENDMCRN)  function  are  executed  without  power  flow  to  coils.    The
ENDMCRN  associated  with  the  Master  Control  Relay  is  used  to  resume  normal  program
execution.    Unlike  Jump  functions,  Master  Control  Relays  can  only  move  forward;  the
ENDMCRN  must  appear  after  its  corresponding  Master  Control  Relay  instruction  in  a
program.

Nested MCR

A Nested Master Control Relay function can be nested completely within another
MCRN/ENDMCRN pair.

There can be multiple Master Control Relay functions with a single ENDMCRN.

The Master Control Relay function has an enable input and a name. This name is used again
with the ENDMCRN. The Master Control Relay has no outputs; there can be nothing after it
in a rung.

Figure 270

With a Master Control Relay, function blocks within the scope of the Master Control Relay
are executed without power flow, and coils are turned off.

The ENDMCRN function must be tied to power rail; there can be no logic before it in the
rung. The name of the ENDMCRN associates it with the corresponding Master Control
Relay(s). The ENDMCRN function has no outputs; there can be nothing after it in a rung.

Figure 271

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Example Master Control Relay and ENDMCRN Functions

In the example, when %I0002 is ON, the Master Control Relay is enabled. When the Master
Control Relay is enabled--even if %I0001 is ON--the Addition function block is executed
without power flow (i.e., it does not add 1 to %R0001), and %Q0001 is turned OFF.

If %I0003 and %I0004 are ON, %Q0003 is turned OFF and %Q0004 remains ON.

Figure 272

23.2.5

Control Functions
Jump, Label

The Nested Jump instruction causes a portion of the program logic to be bypassed. Program
execution continues at the Label specified. When the Jump is active, all coils within its scope
are left at their previous states. This includes coils associated with timers, counters, latches,
and relays.

The Nested Jump instruction has the form ----->>LABEL01, where LABEL01 is the name of the
corresponding nested Label instruction.

A nested Jump can be placed anywhere in a program.

There can be multiple nested Jump instructions corresponding to a single nested Label.
Nested Jumps can be either forward or backward Jumps.

There can be nothing after the Jump instruction in the rung. Power flow jumps directly from
the instruction to the rung with the named label.

CAUTION

To avoid creating an endless loop with forward and backward Jump instructions, a backward
Jump must contain a way to make it conditional.

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Label

The Label instruction is the target of a Jump. Use the Label instruction to resume normal
program execution. There can be only one Label with a particular name in a program.

The Label instruction has no inputs and no outputs; there can be nothing either before or
after a Label in a rung.

Example Jump and Label Instructions

In the example, whenever Jump TEST1 is active, power flow is transferred to Label TEST1.

With a Jump, any function blocks between the Jump and the Label are not executed, and
coils are not affected. In the example, when %I0002 is ON, the Jump is taken. Since the logic
between the Jump and the Label is skipped, %Q0001 is unaffected (if it was ON, it remains
ON; if it was OFF, it remains OFF).

Figure 273

23.2.6

Control Functions
Comment

The Comment function is used to enter a comment (rung explanation) in the program. A
comment can have up to 2048 characters of text. Longer text can be included in printouts
using an annotation text file.

It is represented in the ladder logic like this:

Figure 274

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23.2.7

Control Functions
Drum Sequencer

The Drum Sequencer function is a program instruction that operates like a mechanical drum
sequencer. The Drum Sequencer steps through a set of potential output bit patterns and
selects one based on inputs to the function block. The selected value is copied to a group of
16 discrete output references.

Figure 275

Power flow to the Enable input causes the Drum Sequencer to copy the content of a selected
reference to the Out reference.

Power flow to the Reset input or to the Step input selects the reference to be copied.

The Control Block input is the beginning reference for the Drum Sequencer function’s

parameter block, which includes information used by the function.

Parameters of the Drum Sequencer Function

Input/
Output

Choices

Description

enable

flow

The Enable input controls execution of the function.

Step

flow

The Step input can be used to go one step forward in the sequence.
When the Enable input receives power flow and the Step input makes
an Off to on transition, the Drum Sequencer moves one step. When
Reset is active, the function ignores the Step input.

Reset

flow

The Reset input can be used to select a specific step in the sequence.
When Enable and Reset both receive power flow, the function copies
the Preset Step value in the Control Block to the active Step reference,
also in the Control Block. Then the function block copies the value in
the Preset Step reference to the Out-reference bits. When Reset is
active, the function ignores the Step input.

Pattern R, AI, AQ

The starting address of an array of words, each representing one step
of the Drum Sequencer. The value of each word represents the desired
combination of outputs for a particular value of Active Step. The
number of elements in the array is equal to the length input.

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Input/
Output

Choices

Description

Dwell
Time

R, AI, AQ, none

This optional input array of words has one element for each element in
the Pattern array. Each value in the array represents the dwell time for
the corresponding step of the Drum Sequencer in 0.1 second units.
When the dwell time expires for a given step the Dwell Timeout bit is
set.
If a Dwell Time is specified, the drum cannot sequence into its next step
until the Dwell Time has expired.

Fault
Timeout

R, AI, AQ, none

This optional input array of words has one element for each element in
the Pattern array. Each value in the array represents the fault timeout
for the corresponding step of the Drum Sequencer in 0.1 second units.
When the fault timeout has expired the Fault Timeout bit is set.

Control
Block

The beginning reference address of the

function’s parameter block.

The length of the Control Block is 5 words. A more complete
description of what is contained within this block is listed below.

Length CONST

Value between 1 and 128 that specifies the number of steps.

flow, none

OK is energized if Enable is On and no error condition is detected. If
Enable is Off, this output will always be Off.

OUT

I, Q, M, T, G, R,
AI, AQ

A word of memory containing the element of the Pattern Array that
corresponds to the current Active Step.

Drum
Coil

I, Q, M, T, G,
none

This optional bit reference is set whenever the function block is
enabled, and Active Step is not equal to Preset Step.

Dwell
Timeout

I, Q, M, T, G,
none

This optional bit reference is set if the dwell time for the current step
has expired.

Timeout
Fault

I, Q, M, T, G,
none

This optional bit reference is set if the drum has been in a particular step

longer than the step’s specified Fault Timeout.

First
Follower

I, Q, M, T, G,
none

This optional array of bits has one element for each step of the Drum
Sequencer. No more than one bit in the array is On at any time and that
bit corresponds to the value of the Active Step

Parameter Block for the Drum Sequencer Function

The parameter block (control block) for the Drum Sequencer function contains
information needed to operate the Drum Sequencer.

address

Active Step

address + 1

Preset Step

address + 2

Step Control

address + 3

Timer Control

Active Step

The active step value specifies the element in the Pattern array to copy to

the Out output memory location. This is used as the array index into the Pattern, Dwell
Time, Fault Timeout, and First Follower arrays.

Preset Step

A word input that is copied to the Active Step output when the Reset is On.

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Step Control A word that is used to detect Off to On transitions on both the Step input and
the Enable input. The Step Control word is reserved for use by the function block, and must
not be written to.

Timer Control Two words of data that hold values needed to run the timer. These values are
reserved for use by the function block and must not be written to.

Notes on Using the Drum Sequencer Function

The Dwell Timeout Output bit is cleared the first time the drum is in a new step. This
is true:

—

Whether the drum is introduced to a new step by changing the Active Step or
by using the Step Input.

—

Regardless of the Dwell Time Array value associated with the step
(even if it is 0).

—

During the first sweep the Active Step is initialized.

The Active and Preset Step of the Drum Sequencer’s control block must be initializ

for the Drum Sequencer to work or to pass power flow. Even if the Active Step is in
the correct range (between 1 and length of the Pattern array) and the Preset Step is
not used, the drum will not function if the Preset Step is not in the proper range.

23.3

Data Move Functions

The Data Move functions of the Instruction Set provide basic data move capabilities.

•

MOVE Data. This function copies data as individual bits, so the new location does not
have to be the same data type.

•

Block Move. This function places constants into seven specified memory locations.

•

Block Clear. This function fills an area of memory with zeros.

•

Shift Register. This function shifts one or more data words or data bits from a
reference location into a specified area of memory. Data already in the area is shifted
out.

•

Communication Request (COMMREQ). This important function allows the CPU to
communicate with intelligent modules in the system, for example, communications
modules. The basic format of the COMMREQ function is shown in this chapter. The
detailed parameters needed to program specific communications tasks are
provided in the documentation for each module.

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