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Changing the Load Correction Time

The Load Correction time can be changed within the range 0 to 200µS by sending the new
value in a COMMREQ, as explained later in this chapter.

An example is illustrated below.

In the diagram, T0 is the OFF Time, which is

where

f is the pulse frequency.

T2 = Optical Isolator Delay,

and T1+T2 = ON Time.

Figure 198

18.7

Pulse Train Outputs

Pulse Train Outputs can be used to control stepper motors.

18.7.1

Configuring a Pulse Train Output

Configuring a channel as a Pulse Train Output is done by setting the Channel Function to
Pulse Train in the PLC configuration.

18.7.2

Program References for Pulse Train Outputs

The following program references are assigned for use by Pulse Train Outputs.

Channel 1

Channel 2

Channel 3 Channel 4

Pulse Train Complete

I0494

I0495

I0496

I0511

Enable Output

Q0505

Q0506

Q0507

Q0508

Start Pulse Train

Q0494

Q0495

Q0496

Q0511

Frequency:16 Bit Mode
32 Bit Mode

AQ123

AQ125

AQ127

AQ121

AQ120

AQ123

AQ126

AQ117

Number of Pulses: 16 bit mode
32 Bit Mode

AQ124

AQ126

AQ128

AQ122

AQ 121-122

AQ124-125

AQ127-128 AQ 118-119

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18.7.3

Enabling and Disabling Pulse Train Operation

Pulse Train operation starts when the channel’s Enable Output bit is set to 1 and the
channel’s Start Pulse Train bit transitions from 0 to 1. This automatically clears the Pulse

Train Complete bit to 0. Pulse Train operation continues until the specified number of pulses
have occurred. A Pulse Train Output can be stopped before the requested number of pulses
has been completed by setting its Enable Output bit to 0. If the Enable Output bit transitions
from 1 to 0, the Pulse Train stops immediately. When the last pulse is completed, the

channel’s Pulse Train Complete bit goes to 1.

A Pulse Train Output continues to operate when the Micro PLC goes from Run mode to Stop
mode. If a Pulse Train Output is running when power is lost, it will restart after power is
restored when the PLC transitions with Run mode if both the Enable Output bit and the Start
Pulse Train output bits are set to 1.

18.7.4

Setting Up the Pulse Frequency

The application program sets up the frequency of a Pulse Train Output by writing a value to

the channel’s Frequency reference. The frequency range is 15Hz to 65kHz for Micro 20

-/40-

/64- PLCs, and 15Hz to 5kHz for other models).

The sum total of frequency configured for all Pulse Train Outputs on a Micro PLC should be
less than or equal to 65kHz (this frequency is available for a Micro-20/40/64 only). The
minimum frequency that can be configured on each channel is 15Hz. For example: If all the
channels are to be configured for Pulse Train with Ramp for maximum possible frequency,
the frequencies on each channel can be 15kHz, 15kHz, 15kHz, and 20kHz.

The frequency of a Pulse Train Output can be changed while the Pulse Train is operating.
One application of this feature would be to ramp up at the beginning of the Pulse Train
operation, and ramp down at the end. For a Micro-20, -40, -64 PLC, Pulse Ramping can also
be done by configuring the channel for Pulse Train with Ramp.

The actual frequency output can have a tolerance of 1%.

If the maximum count speed is more than 30 kHz for a Type B Counter, or more than 60 kHz
for Type A, resistance must be added to the encoder input as shown in the example below:

Figure 199

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18.7.5

Setting Up the Number of Pulses

The application program sets up the number of pulses to be output (0 to 65535) by writing

the value to the channel’s Number of Pulses reference.

18.7.6

Load Correction Time

Pulse Train Outputs have a nominal duty cycle of 50%, but the PLC optical isolators can skew
the duty cycle, depending on temperature and load. To compensate for this, the PLC applies
an additional load correction time to the zero-output time of each pulse. The default load
correction time depends on the Micro PLC type. The default times are: 2µS for 20-/40-/64-
point Micro PLCs with DC outputs, 35µS for other Micro PLCs with DC outputs, 10µS for 20-
/40-/64-point Micro PLCs with relay outputs, or 85µS for other Micro PLCs with relay outputs

Changing the Load Correction Time

The Load Correction time can be changed within the range 0 to 200µS by sending the new
value in a COMMREQ, as explained later in this chapter.

An example is illustrated below.

In the diagram, T0 is the OFF Time, which is

where

f is the pulse frequency.

T2 = Optical Isolator Delay, and

T1+T2 = ON Time.

Figure 200

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18.8

Pulse Train with Ramp

The Pulse Train with Ramp feature of Micro-20, -40, and -64 PLCs combines the basic
operation of a Pulse Train Output with configurable acceleration and deceleration times to
produce Pulse-Train profile like the example shown below.

Figure 201

18.8.1

Configuring Pulse Train with Ramp

An output can be set up as a Pulse Train with Ramp by selecting 4 Type A or 1 Type A / 1 Type
B as the Counter Type and selecting Pulse Train with Ramp as the Channel Function.

A Pulse Train with Ramp has configurable acceleration and deceleration rates. The default
for both is 1,000,000 (the maximum). Both acceleration and deceleration can be selected
during configuration from the range of 90 to 1,000,000. Acceleration and deceleration do
not need to be the same. Appropriate values depend on the application and the capability
of the stepper motor being driven by the module. Acceleration and Deceleration can also
be temporarily changed from the application program.

18.8.2

Program References for Pulse Train with Ramp Outputs

The following program references are used by Pulse Train with Ramp Outputs (Can only be
configured in 4TypeA/1TypeA 1TypeB configuration).

Output 1

Output 2

Output 3

Output 4

Pulse Train Complete

I0494

I0495

I0496

I0511

Start Pulse Train

Q0494

Q0495

Q0496

Q0511

Enable Output

Q0505

Q0506

Q0507

Q0508

Frequency

AQ123

AQ125

AQ127

AQ121

Number of pulses

AQ124

AQ126

AQ128

AQ122

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18.8.3

Setting Up the Pulse Frequency for Pulse Train with
Ramp

The application program sets up the frequency of a Pulse Train with Ramp by writing a value

to the channel’s Frequency reference. The frequency range is 15Hz to 65kHz.

The sum total of frequency configured for Pulse Train with Ramp channels should be less
than or equal to 65kHz. The minimum frequency that can be configured on each channel is
15Hz. For example: If all the channels are to be configured for Pulse Train with Ramp for
maximum possible frequency, the frequencies on each channel can be 15kHz, 15kHz,
15kHz, and 20kHz.

The frequency, acceleration, deceleration, and number of counts of a Pulse Train with Ramp
cannot be changed when the ramp output has started. If the frequency is changed in the
%AQ references after the ramp output has started, the new frequency is used for the next
ramp that is generated.

The actual frequency output can have a tolerance of 1%.

18.8.4

Setting Up the Number of Pulses

The application program sets up the number of pulses to be output (0 to 65535) by writing
the value to the cha

nnel’s Number of Pulses reference.

18.8.5

Changing the Acceleration and Deceleration

Acceleration and deceleration are set up in the channel configuration. The configured
acceleration and deceleration can also be temporarily changed in the rage of 90 to 1,000,00
using a COMMREQ in the application program, as explained later in this chapter.
Acceleration and deceleration cannot be changed while the function is operating.

18.8.6

Controlling Operation of a Pulse Train with Ramp Output

A Pulse Train with Ramp starts when th

e channel’s Enable Output bit is 1 and the channel’s

Start Pulse Train bit transitions from 0 to 1.

When the Pulse Train begins, the channel’s Pulse Train Complete bit is set to 0. The channel

outputs the specified number of pulses in varying pulse widths, to produce a velocity profile

similar to the one shown below. After the last pulse is completed, the channel’s Pulse Train

Complete bit is set to 1.

After a Pulse Train with Ramp function has started, it continues until either all of its pulses
have been generated or its Output Enable bit changes from1 to 0.

The ramp up or ramp down motion occurs in steps of 100ms; so the velocity gradient
changes every 100ms until the desired frequency is reached (provided there is a sufficient
number of pulses to ramp up to the desired frequency).

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Figure 202

For the example above, the ramp up time is 500ms (1/2 second), so the ramp up takes place
in 5 steps: 100ms, 200ms, 300ms, 400ms, 500ms with frequencies of 1kHz, 2kHz, 3kHz,
4kHz, and 5kHz respectively.

The application program can stop a Pulse Train with Ramp before the requested number of
pulses has been completed by setting its Enable Output bit to 0. When the Enable Output
bit transitions from 1 to 0, the output starts decelerating. The channel outputs a number of
pulses based on: (1) the configured deceleration and (2) the velocity at the time the Enable

Output bit goes Off. When the last pulse is completed, the channel’s Pulse Train Complete

bit is set to 1.

Stop Ramp with Deceleration

If the Enable Bit set to 0 during the “at velocity” part of the Pulse Train, the output ramps

down normally as shown at left below. If the Enable Bit is set 0 during the acceleration
phase, ramping up stops and ramping down begins immediately as shown at right. The
deceleration occurs at the configured or commanded rate.

Figure 203

If the Ramp output is already decelerating (because the number of pulses has been
reached) when the Enable Output bit transitions from 1 to 0, the Pulse Train output
continues decelerating at the same rate.

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Stop Ramping Immediately

When the Micro PLC powers up or receives a new configuration, it automatically sets up all
Ramp channels to decelerate when the Output Enable bit goes to 0.

If a Pulse Train with Ramp output should stop immediately, a COMMREQ can be used, as
described later in this chapter.

18.9

COMMREQs for the HSC/PWM/PTO Functions

The application program can use the COMMREQ function to provide data or send the
following commands to High-Speed Counters, Pulse Train outputs, or PWM outputs that are
currently enabled:

•

Load Accumulator

•

Load High and Low Limits

•

Load Accumulator Increment

•

Set Counter Direction

•

Load Timebase

•

Load ON and Off Presets

•

Load Preload

•

Load Stop Mode or Resume Decelerate Mode (for Micro-20, -40, -64 CPUs only)

•

Load Acceleration and Load Deceleration (for Micro-20, -40, -64 CPUs only)

•

Load Correction

Program logic should be set up to assure that the command is sent to the module once, not
repeatedly. These changes are temporary; they lost when the PLC is powered down and
when a new configuration is stored from the programmer.

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18.9.1

The COMMREQ Command Block

The command data must be placed in the correct order (in a command block) in CPU
memory before the command is executed. The command block is composed of 14 words
as shown below. All values are hexadecimal unless otherwise indicated. The command block
can be placed in any word-oriented area of memory that is not reserved (see Chapter 22: for
a list of reserved areas).

Offset

Data

Description

address

0004

Always 0004

address +1

don’t care

Not used (always zero). The Micro PLC ignores the Wait flag for all
COMMREQ junctions.

address +2

don’t care

not used

address +3

don’t care

not used

address +4

don’t care

not used

address +5

don’t care

not used

address +6

don’t care

not used

address +7

don’t care

not used

address +8

0008

Data type (8 = registers)

address +9

000A

Start location of Command Word

–

1 (%R0011)

address +10

nnnn

Command Word (see next page)

address +11

nnnn

LS Data Word

address +12

nnnn

MS Data Word used only for ramping in 4 Type A 32-bit or
One Type A, One Type B 32-bit mode in Micro 20-/40-/64-CPU.
Not used by other Micro PLCs

Contents of the Command

The last three words of the Command contain the command parameters. These words are
treated as independent bytes. They can be entered in hexadecimal or decimal format. The
format for the last three words is:

Figure 204

The Command Word, located at “address +10” of the command, identifies the

action to be

performed. The MSB of the command word specifies the channel number (1

–

4 for Type

A, always 1 for Type B).

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Example:

To set Counter 1 to 1234H, load command registers with:

Command word:

0101

LS data word:

1234

MS data word:

Example:

To set Counter 1 to 200,000 (30D40H) in 32-bit mode, load command
registers with:

Command word:

0101

LS data word:

0D40

MS data word:

0003

Negative values must be entered in 32-

bit two’s complement format.

Example:

To set the Load Preload to a value of

–

1000 decimal,

enter the hex value FFFF FC18 for command word 01nF.

Command
Word (hex)

Command Description

0n01

Load
Accumulator

Loads any value within a counter’s limits directly into the

Accumulator. If a count is received at the same time, the count is lost.

0n02

Load High
Limit

Sets the High and Low limit to any value in the counter range. Move
the Low Limit first when shifting down or the High Limit first when
shifting up. Loading limits in the wrong order can cause an error. The
command is successful if all parameters are within the new range.

0n03

Load Low
Limit

0n04

Load
Accumulator
Increment

Offsets a counter Accumulator by up to +127 or

–

128 counts. Only

the LSB data is used with this command. This can be done at any time,
even while the counter is counting at maximum rate. However, if a
count is received at the same time the CPU updates the Accumulator
value, the count is lost. If the offset causes the counter to exceed its
limits, this parameter is rejected.

0n05

Set Counter
Direction

(Type A only) Changes the count direction. Only the LSB of the first
data word is used for this command (00 = up, 01 = down).

0n06

Load
Timebase

Changes the time interval used for the counts/timebase word data.
The range is 10 to 1000mS in 10mS intervals.

0n0B

Load ON
Preset

Sets up the output turn on points within the counter range. There is
one output associated with each counter. See the previous
information about Presets for appropriate settings.

0n15

Load OFF
Preset

Sets up the output turn off points within the counter range. There is
one output associated with each counter. See the previous
information about Presets for appropriate settings.

0n1F

Load
Preload

Changes the count value loaded into the counter Accumulator when
the Preload input is activated.

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Command
Word (hex)

Command Description

0n3B

Load Stop
Mode (or
Resume
Decelerate
Mode)

(Micro-

20/40/64 CPU only) Changes a Pulse Train output’s

deceleration to stop the Ramp immediately when the Output Enable
bit goes Off. The Ramp function must be enabled.
The same command can be used to reset the output to Decelerate
mode (the default) by entering the value 0001 in the LS data word.

0n3C

Load
Acceleration

(Micro-

20/40/64 CPU only) Changes a Pulse Train output’s

acceleration. The Pulse Train with Ramp function must be enabled.
For channels 1

–

3, acceleration and deceleration can be selected

from  the  range  of 10  p/s2  to 1,000,000  p/s2.    For  channel  4,  the
range  is  90 p/s2  to  1,000,000  p/s2  .    The  default  for  both  is
1,000,000.
In the acceleration and deceleration commands, the data value is a
32-bit  number.  These  are  the  ONLY  Data  Commands  that  should
have any value other than 0 in the MS data word.
Example: to change the acceleration rate of Pulse Train output 1 to
200,000

(30D40H),

load:

Command

word:

013C

data

word:

0D40

MS data word: 0003

0n3D

Load
Deceleration

(Micro-

20/40/64 CPU only) Changes a Pulse Train output’s

deceleration. The Ramp function must be enabled. See Load
Acceleration above for details.

0n3E

Load
Correction

Sets the change (in µS) that should be applied to the duty cycle of a
Pulse Train output to compensate for the slow turn-off time of the
optical isolator circuit (35µS

–

DC outputs; 85µS relay outputs). The

range is 0 to 200µS.

Note:

If a Load Accumulator command is executed with the ON Preset value, the Preset will be turned on
for that instance only.

If a Load Accumulator command is executed with the OFF Preset value, the Preset will be turned
off for that instance only.

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18.9.2

COMMREQ Example

The example uses a COMMREQ to load the value 1234 into the Accumulator for Counter 3.

Figure 205

The first rung in the example includes a one-shot coil (%T0002) that executes the COMMREQ
once. This prevents multiple messages from being sent.

The next rung uses a Block Move Word function to load the commands. In this example,
%R0101 through %R0114 are used for the COMMREQ Command Block. Any registers can be
used.

The COMMREQ function has four inputs and one output.

Parameter

Description

enable

%T0002 to enables the COMMREQ function.

Points to the starting address of the Command Block, which is %R0101.

SYSID

Indicates which rack and slot to send the message to (physical location of HSC
module). The SYSID is always 0004 for the Micro PLC.

TASK

This parameter is ignored and should be set to zero.

This output is energized if an error is detected during processing of the
COMMREQ.

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Command Word Error Responses

If the module receives an invalid command parameter in a Command Word, it returns an
error code in the first word of its word input (AI) data. The following error codes are used for
High-Speed Counter COMMREQs:

Note:

If the program issues a COMMREQ that changes count direction, the counter will go immediately
into the new mode. Remember that the output does not change states at exactly the same points
on an Up-counter as it does on a Down-counter.

Error Code

Description

Definition

Decimal

Hex

Invalid Command

Command number received was invalid for
the HSC.

Invalid Counter Number or
Channel

Counter number in the Data Command
Word was not a valid counter based on the
current configuration.

Counter/Channel 1 Limit Error Invalid Low or High limit value

New limit places Preload value out of range
New limit places Off Preset out of range
New limit places Accumulator value out of
range
Accumulator value is out of range
Preload value is out of range
On Preset value is out of range
Off Preset value is out of range

Counter/Channel 2 Limit Error

Counter/Channel 3 Limit Error

Counter/Channel 4 Limit Error

Load Stop Mode/Reset
Decelerate Mode

Invalid value. Must be 1 (decelerate) or 2
(stop).

Load Acceleration

Acceleration too low. Must be > 10 for
channels 1-3 and >90 for channel 4.

Load Acceleration

Acceleration

too

high.

Must

< 1,000,000

Load Deceleration

Deceleration too low. Must be > 10. for
channel 1-3 and >90 for channel 4.

Load Deceleration

Deceleration

too

high.

Must

< 1,000,000

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18.10

HSC Application Examples

18.10.1

RPM Indicator

The HSC can be used as a position/motion indicator when connected to a feedback device
(such as an encoder) that is coupled to a rotary motion. RPM indication can be obtained

directly from the counter’s Counts/Timebase register (CTB) or derived from it by a simple

calculation.

The RPM calculation is:

where:

CTB =

counts/timebase reading from the counter

PPR =

pulses/revolution produced by the feedback device

T =

timebase expressed in minutes

If the number of pulses per revolution is an integer power of 10, setting the timebase for 6,
60, 600, 6000, or 60,000 produces a direct reading of RPM in the Counts per Timebase
register with an assumed decimal placement.

Example

If feedback produces 1000 pulses/revolution, CTB reading = 5210, and the timebase is
configured for 60ms, which gives:

T = 60/60000 = .0001 and 1/T = 1000.

The Counts per Timebase reading equals 521 and

CTB reading is RPM with 1 RPM resolution.

Input Capture

The High-Speed Counter strobe inputs can act as pulse catch inputs for inputs 2, 4, 6, and 8
by using the Strobe Status bits as a latch.

To use this feature:

Configure a Type A Counter on any channel.

Set the Preload//Strobe parameter to “Strobe”.

The corresponding Strobe Status bit will be latched if there is a pulse of at least 100 µsec in
width. The Reset Strobe bits can be used as clear functions for the latched status bits.

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Chapter 19:

Motion Control Functions

Micro-20, Micro-40 and Micro-64 PLCs (release 3.6 or later) can perform basic Motion
Control functions of Jogging, Homing, Blended Move, and Stop Motion. This chapter
describes the use of motion control functions.

•

Overview

—

Program References for Motion Features

—

Position Registers

—

Function Block Instance Registers

—

Error Codes for Motion Features

•

Finding a Home Position

—

Find Home Function Block

—

Stopping Find Home

—

Example Program Logic for Find Home

•

Moving to the Home Position

Go Home Function Block

Stopping Go Home

Example Program Logic for Go Home

•

Jogging

—

Jogging Function Block

—

Stopping Jogging

—

Example Program Logic for Jogging

•

Blending

—

Blending Function Block

—

Stopping Blending

—

Example Program Logic for Blending

—

Examples of Blended Moves

•

Stopping Motion on an Axis

—

Stop Motion Function Block

—

Example Program Logic for Stop Motion

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19.1

Overview

The High-Speed Counter outputs of a Micro-20, Micro-40. or Micro-64 PLC can be
independently configured for motion support. Use of these features requires PAC Machine
Edition version 5.5, SP2, SIM 6 or later.

The channel’s configured HSC/PWM/PTO setting mu

st be either 4 Type A_32, or 1 Type A /

1 Type B_32. The

channel’s Counter Function must be configured as Motion Support.

Configuration is described in Chapter 16:.

Function blocks can be used in the application program to set up and control motion
operations. The same function blocks supply additional parameters for the operation.

19.1.1

Program References for Motion Features

Output 1

Output 2

Output 3

Output 4

Position Register (REAL)

AI006-007

AI010-011

AI020-021

AI024-025

Mode Select Bit (BOOL)

Q497

Q498

Q499

Q500

Rotary Mode High Limit Register
(DWORD)

AQ117-118 AQ121-122 AQ125-126

AQ113-114

Rotary Mode Low Limit Register (REAL) AQ119-120 AQ123-124 AQ127-128

AQ115-116

Motion Enable (BOOL)

Q505

Q506

Q507

Q508

Axis error register (WORD)

AI002

AI003

AI004

AI005

Axis error reset bits (BOOL)

Q489

Q490

Q491

Q492

19.1.2

Position Registers

The Micro PLC stores the cumulative motor position in the

channel’s Position Register,

where it can be read from the application program. The capacity of the Position Register is
a 32-bit real value. When used for motion support, the 32-bit Position Registers are used as
shown in the table above.

All  commanded  moves  increment  or  decrement  the  value  in  the  Position  Register,  so  it
reflects the actual motor position. For example, the Position Register is set at 0.  A 10,000-
count move is commanded in the forward direction.  At the end of this move, the Position
Register contains the value 10,000.  Now a 2,000-count move is commanded in the reverse
direction.  At the end of this move, the Position Register contains the value 8,000 (10,000

–

2,000).

The Position Register is automatically cleared: at power-up, when a new configuration is
downloaded, when PLC memory is cleared, when the configuration is cleared, and when the
CPU transitions from STOP to RUN mode. It is set to zero after a successful Find Home
operation. When the Position Register is cleared, the cleared value appears in the reference
memory window only when the PLC is put into RUN mode.

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Operating Modes of the Position Registers

The position register can function in either Rotary mode or Linear Mode.

Rotary Mode Operation of the Position Registers

In Rotary mode, the Position Register wraps when the configured high limit or low limit is
reached and continues incrementing or decrementing based on the direction of operation.
Rotary mode is selected by setting output bit %Q497, Q498, Q499, or Q500 to 1, for channel
1, 2, 3, or 4, respectively. The high limit and the low limits for Rotary mode can be set up
using the references shown on the previous page.

Position Register transitions for both clockwise and counterclockwise motions always start
at the configured low limit. For example, if the low limit = -100.0 and the high limit = +100.0,
a movement of 5 units in the clockwise direction sets the Position Register value to

–

95.0,

and a movement of 5 units in the counter-clockwise direction sets the position register value
to +96.

If the configured High Limit is less than the Low Limit, the error is displayed in
%AI0001/2/3/4 memory for each of the channels and the High Limit defaults to the Low
Limit +1.

Linear Mode Operation of the Position Registers

In Linear mode, any configured Rotary limits are not used. The Position Registers increment
or decrement from zero after power-up, and on every Stop to Run transition. At other times,
the Position Registers increment or decrement from the last move position.

Output bits %Q0497-Q0500 can be used to provide inputs for this mode for each of the four
channels respectively. A value of 0 selects Linear mode and 1 selects Rotary mode.

Limits of the Position Register value in Linear mode are +3.4e38 and

–

3.4e38. If either limit

is reached, the value stops changing.

19.1.3

Function Block Instance Registers

Figure 206

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