SMAC LAC-26 Product manual

1
SMAC
LAC-26
T ECHNICAL R EFERENCE M ANUAL
Revision 0, April 2013
SMAC CORP.
5807 Van Allen Way
Carlsbad, CA 92008

2
S.M.A.C.
5807 VAN ALLEN WAY
CARLSBAD, CA 92008
PHONE: [phone] / FAX: [phone]
FOR TECHNICAL ASSISTANCE CALL : 1-760-929-7575
© C OPYRIGHT A UTOMATION M ODULES , I NC . 1993 - 2013

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TABLE OF CONTENTS
1. Introduction............................................................................................................................... 3
1.1 Specifications........................................................................................................................ 4
1.2 Digital I/O Interface............................................................................................................. 5
1.2.1 Dedicated Digital Inputs ............................................................................................... 5
1.2.2 General Purpose Inputs ................................................................................................. 5
1.2.3 General Purpose Outputs .............................................................................................. 6
1.2.4 Digital I/O "States" ....................................................................................................... 6
1.2.5 I/O Technical Specifications......................................................................................... 7
1.3 Encoder Interface ................................................................................................................. 7
1.4 Output Driver Interface........................................................................................................ 8
1.5 Analog to Digital Conversion (A/D) Interface .................................................................... 8
1.6 Serial Interface ..................................................................................................................... 8
2. Macro Interrupt System.......................................................................................................... 8
2.1 The Interrupt Vector Table .................................................................................................. 9
2.2 Enabling and Disabling Interrupts ....................................................................................... 9
2.3 Interrupt Sources.................................................................................................................. 9
2.4 Interrupt Priority ................................................................................................................ 10
2.5 Interrupt Completion.......................................................................................................... 10
2.6 Interrupt Latency................................................................................................................ 10
3. Entering Commands.............................................................................................................. 11
3.1 Downloading Commands................................................................................................... 12
4. Introduction to Commands................................................................................................... 12
4.1 Parameter Commands ........................................................................................................ 12
4.2 Reporting Commands ........................................................................................................ 21
4.3 Motion Commands............................................................................................................. 27
4.4 Register Commands ........................................................................................................... 33
4.4.1 Internal Variables........................................................................................................ 33
4.5 Sequence Commands......................................................................................................... 41
4.6 Learned Position Storage (LPS) Commands ..................................................................... 46
4.7 Macro Commands.............................................................................................................. 47
4.8 Input / Output (I/O) Commands......................................................................................... 51
4.9 Future Expansion Interface ................................................................................................ 53
4.10 Serial Communications and Miscellaneous Commands.................................................. 54
5. AMC driver setup ................................................................................................................... 63
5.1 Communication Protocol .................................................................................................... 63
5.1.1 CANopen ..................................................................................................................... 63
5.1.2 RS-485 Communication............................................................................................... 63
5.2 Control Modes .................................................................................................................... 64
5.2.1 Current (Torque) or Profile Current (Torque) ............................................................. 64
5.2.2 Velocity or Profile Velocity......................................................................................... 64
5.2.3 Position or Profile Position .......................................................................................... 64
5.2.4 Cyclic Synchronous Modes ......................................................................................... 64
5.2.5 Feedback Supported..................................................................................................... 65
5.2.6 Feedback Polarity......................................................................................................... 65
5.2.7 Hall Sensors ................................................................................................................. 65
5.2.8 Encoder Feedback........................................................................................................ 66

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5.2.8 ±10 VDC Position........................................................................................................ 67
5.3 Command Sources .............................................................................................................. 67
5.3.1 ±10V Analog................................................................................................................ 67
5.3.2 Encoder Following....................................................................................................... 67
5.3.3 Over the Network......................................................................................................... 68
5.3.4 PWM and Direction ..................................................................................................... 68
5.3.5 Indexing ....................................................................................................................... 68
5.3.6 Jogging......................................................................................................................... 68
5.3.7 5V TTL Step and Direction (DZR Drives Only) ......................................................... 68
5.4 System Requirements.......................................................................................................... 68
5.4.1 Specifications Check.................................................................................................... 68
5.4.2 Motor Specifications.................................................................................................... 69
5.4.3 Power Supply Specifications ....................................................................................... 70
5.4.4 Environment................................................................................................................. 72
6. Operation and Features.......................................................................................................... 73
6.1 Features and Getting Started............................................................................................... 73
6.1.1 Initial Setup and Configuration.................................................................................... 73
6.1.2 Commutation................................................................................................................ 74
Appendix 1. Specification........................................................................................................... 77
Appendix 2 Outline drawing...................................................................................................... 78
Aooendix 3. Connector Pin Definitions.................................................................................... 80
Appendix 4 – Summary of LAC-26 Commands ...................................................................... 81
Appendix 5 AMC Driver Troubleshooting............................................................................... 82

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1. Introduction
The LAC-26 is a two axis stand-alone integrated controller / driver, with input / output (I/O) capabilities
similar to the LAC-25. The first axis is for the control of DC brush type motors or actuators with its
integrated driver. The second axis features a high power driver for 3 phase brushless, single phase
bushed, and voice coil inductive load motors.
The LAC-26 implements a mnemonic type command instruction set via a standard RS-232 serial
communications interface. These commands can be executed directly or used to create command
macros which are stored in the onboard nonvolatile RAM (NVRAM).
The LAC-26 can interface to the real world via the onboard motor drivers, 2 channels of
quadrature type encoder interface, 4 channels of optoisolated digital input and 2 channels of optoisolated
digital output, with additional optoisolated inputs serving for limit, home and fault functions, 5 channels of
10-bit analog to digital (A/D) conversion (2 of which are reserved for monitoring amplifier output current),
and an RS-232 serial communications link. A proprietary RS-422 interface is provided for future I/O
expansion modules.
The LAC-25 controller card embedded within can control Digi Flex servo driver through the following I/O
ports. Digital Output 2 – starting auto commutation signal, Digital Output 3 – enable driver, Digital Input 3
– commutation successful signal from driver, and axis 2 analog output – commutation.

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1.1 Specifications
Description Stand-Alone 2 Axis Servo Motor Controller / Driver
Operating Modes Position, Velocity, Torque, Electronic Gearing
Control Algorithm PID
Max. Servo Loop Rate 100 µS per enabled axis
Servo Position Feedback Incremental Encoder with Index
Output (Standard) PWM Motor Drive, Single Phase (brushed), 3 Amps Cont. and 6 Amps Peak at
50 VDC Max.
PWM Frequency Approximately 19.531 KHz
Encoder and Index Input 5V Single-ended or Differential
Encoder Supply Voltage 5 VDC
Encoder Count Rate 2 Million Quadrature Counts per Second
Position Range 32 Bits
Velocity Range 32 Bits
Acceleration Range 32 Bits
General Purpose Digital I/O 3 Optoisolated inputs, 2 Optoisolated outputs
Dedicated Digital Inputs Limit+, Limit-, Home and Fault, for each axis
Analog Inputs 5 Channels With 10-Bit Resolution, 3 are user accessible
Analog Output2 1 Channels, with 12-bits Resolution, ±10 VDC
Expansion I/O Optional Expansion to 64 I/O
Communication Interface RS-232
Supply Voltage +11 To +50 VDC
Motor Voltage +12 To +48 VDC
Dimensions 226mm Long by 88mm wide by 73mm Thick
Weight Approximately 1.2 Kg
2nd Axis Driver Specification
Description DigiFlex Servo Drive
Operation Mode Current Loop(50 us), Velocity Loop(100 us), Position Loop(100 us)
Command Source ±10 V Analog, 5V Step and Direction, Encoder Following, PWM and Direction
Feed Back Support Incremental Encoder (Max 20 MHz Quadrature), Halls, ±10VDC Position, Aux
Incremental Encoder
Commutation Methods Sinusodal, Trapezoidal
Output (Motor Supported) Single Phase Brushed, Voice Coil, Inductive Load ;
Three Phase (Brushless); 12A peak, 6A Continuous current
Communication Interface RS-232, RS-485
Supply Voltage +20 To +80 VDC
Logic Supply Voltage 5 VDC
Option 1
st
axis Configured

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1.2 Digital I/O Interface
The LAC-26 includes 4 channels of general purpose digital input and 4 channels of general
purpose digital output. Additionally, there are four channels of dedicated digital input for each of the two
axis'. All of these I/O are protected through the use of optoisolators.
1.2.1 Dedicated Digital Inputs
Figure 1 illustrates one of the LAC-26’s dedicated digital inputs. These inputs are Limit+, Limit-,
Home and Fault for both axis of the LAC-26. The power to activate these inputs is provided by the LAC-
26 so it is only necessary to complete the circuit to activate the input.
The Limit inputs are intended for signaling the LAC-26 that an axis has reached it’s end of travel.
When such an event occurs, the LAC-26 can ignore the event or stop the servo in some controlled
fashion. The Home input is for detecting some sort of "home position" sensor. This can be used with the
encoder index input to implement a very accurate homing method. A typical use for the Fault input is for
an external device to signal a fault condition such as over-temperature.
Note: The external Fault input is tied to the internal over-temperature signal from the onboard drivers.
When a fault condition occurs, that is either the internal over-temperature signal or external Fault
signal go active, the 16-bit internal variable FCNT (see Internal Variables) begins to increment at 1
rate of once per millisecond. If the fault condition clears then the FCNT variable is also cleared. If
the fault condition remains present long enough for the FCNT variable to count up to the value
assigned to the FCMP variable, then the over Fault bit in the status word will be set and the servo
will be disabled (assuming the Fault interrupt has not been enabled). The default value for FCMP
is 10000 which will give a 10 second delay before causing the Fault bit to be set.
Figure 1. LAC-26 Dedicated Input.
1.2.2 General Purpose Inputs
Figure 2 illustrates one of the LAC-26’s general purpose inputs. These inputs are galvanically
isolated from the LAC-26. Current of the proper polarity must be supplied to the circuit to activate the
input.
Figure 2. LAC-26 General Purpose Inputs

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1.2.3 General Purpose Outputs
Figure 3 illustrates one of the LAC-26’s general purpose outputs. These outputs are galvanically
isolated from the LAC-26. When an output is activated, positive current will flow from the collector of the
optocoupler transistor (the output pin) to it’s emitter (the output return pin),
Figure 3. LAC-26 General Purpose Output
1.2.4 Digital I/O "States"
There are several commands that deal with controlling the digital I/O. All of these commands
operate based on the following philosophy: With regard to an input, "active" means there is sufficient
current flowing through that input and "inactive" means there is lack of sufficient current through that
input. With regard to outputs, "active" means the ability for an output to pass current and "inactive" means
the inability for an output to pass current.
The Channel High (CH) and Channel Low (CL) commands provide the user with the ability to
determine whether a channel is active in the "on" state (CH) or active in the "off" state (CL). This is
analogous to a switch and to whether it is normally open or normally closed. The Channel On (CN) and
Channel Off (CF) commands do exactly as they imply in that they will turn a given output either on or off,
which will make that output either active or inactive depending on the CH and CL commands as stated
previously.
The (CH) command causes the following interpretation of the inputs and outputs:
An "activated" output is considered to be ON (e.g., Channel On “CN” command).
An "inactivated" output is considered to be OFF (e.g., Channel Off “CF” command).
An "activated" input is considered to be ON (e.g., Do If On “DN” command).
An "inactivated" input is considered to be OFF (e.g., Do If Off “DF” command).
The (CL) command causes the following interpretation of the inputs and outputs:
An "activated" output is considered to be OFF (e.g., Channel Off “CF” command).
An "inactivated" output is considered to be ON (e.g., Channel On “CN” command).
An "activated" input is considered to be OFF (e.g., Do If Off “DF” command).
An "inactivated" input is considered to be ON (e.g., Do If On “DN” command).
Input Current “CH” “CL” Output Current “CH” “CL”
Flowing On Off Flowing CN CF
No Flow Off On No Flow CF CN

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Table 2. I/O States.
Another feature of the digital input system is the ability for software input debouncing. All of the
general purpose digital inputs are automatically sampled once every millisecond. Depending on the
debounce delay set by the Input Debounce (ID) command, a given input must remain in the same state
during one or more samplings before it is considered valid. If an input were to be found in a changed state
during a sampling, the input would become invalid and the debounce delay would be restarted. If no or "0"
debounce delay is used, then no input debouncing is performed. For example: if a "ID5" command has
been issued, then a given input must remain in the same state for 5 samplings or for 5 milliseconds.
1.2.5 I/O Technical Specifications
1.2.5.1 General Purpose I/O Nominal Specifications.
Unit Specification
5 V Minimum voltage to activate input.
0.83 mA Input current at minimum activation voltage.
24 V Maximum input voltage.
4.87 mA Input current at maximum voltage.
1.1 V Maximum voltage to deactivate input.
6 V Absolute maximum reverse input voltage.
40 V Maximum voltage output can sustain.
100 mA Maximum current output can sustain.
Table 3: General Purpose I/O Specifications
1.2.5.2 Dedicated I/O Nominal Specifications.
Unit Specification
10
Ω
Maximum external circuit resistance to activate
input.
1
K Ω
Minimum external circuit resistance to deactivate
input.
Table 4: Dedicated I/O Specifications
1.3 Encoder Interface
The LAC-26 has two channels of quadrature type encoder interface with optional index signal
input and the ability to supply +5 VDC at a minimum of 50 mA (or greater depending on other demands
put on the internal 5 VDC power supply). The phase A+ and phase B+ inputs are pulled up to +5 VDC
with 2.7K resistors, and the phase A- and phase B- inputs a biased at +2.5 VDC with 2.7K resistors. This
arrangement which will accommodate both open collector and totem pole single-ended output encoders
or differential output encoders. The phasing of the channels as well as the index signal sense can be
changed via program command.

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1.4 Output Driver Interface
The LAC-26 onboard output drivers are PWM switching amplifiers capable of supplying 3 Amps
continuous and 6 Amps peak (for 200 mS minimum) at a switching frequency of approximately 19.531
KHz. These drivers are intended for driving DC brush type motors or actuators. Both drivers share the
main power supply input and the peak voltage output to the motor will be nearly that of what is supplied.
The output drivers include an over-temperature sensor. If this sensor determines that the
amplifier’s temperature is greater than 140° C, the amplifier will then be disabled and the Over-
Temperature bit will be set in that axis' status word.
For applications requiring capabilities above those of the onboard drivers, the ability to interface
to external drivers is provided. This consists a 12-bit D/A ±10 VDC analog output signal for each axis. In
applications where external drivers are not required, the analog outputs can be used for other purposes
(e.g.,: oscilloscope monitoring of following error or output command).
1.5 Analog to Digital Conversion (A/D) Interface
The LAC-26 provides a 5 channel, 10 bit A/D conversion interface with a +10 VDC reference and
analog ground. For reverse compatibility purposes the A/D interface is actually ten channels but
the user is only given access to channels 0, 1 and 2 while channels 6 and 7 are used internally for
monitoring the output current of the onboard drivers. The other channels are unavailable and
should be ignored.
Whenever a Tell Analog "TA" or Get Analog "GA" command is issued, the specified A/D channel
is converted and the result is either reported or stored for access by the user. Also, whenever the servo
loop for an axis is executed, the "current monitoring" channel for that axis is converted and the result is
stored for later access.
1.6 Serial Interface
The LAC-26 communicates with a host computer or a "dumb" terminal via an RS-232 serial
interface. The baud rate is user selectable from 300 to 19,200 baud with 9600 baud being the default.
Characters are fixed at 8 bits in length with 1 stop bit and no parity. Software XON / XOFF handshaking is
provided. Hardware handshaking is not supported at this time.
2. Macro Interrupt System
The LAC-26 employs a "Macro Interrupt System" to provide additional versatility in programming
the LAC-26. This system comprises 32 interrupt sources with corresponding vectors. When an interrupt's
source is enabled for operation and then becomes active, the current macro being executed is saved to a
so called macro stack and execution of the macro specified by that interrupt's vector table entry begins.
This happens to be similar procedure to that which the Macro Call (MC) command follows.

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2.1 The Interrupt Vector Table
The Interrupt Vector Table consists of an entry for each interrupt source and each entry will
correspond to that interrupt's level (level 0 = entry 0, level 1 = entry 1, etc.). A particular table entry must
be loaded with the number of a valid macro to be executed should that interrupt source become active.
The method for loading a vector table entry is provided by the Load Vector (LV) command. The user must
first use the Accumulator Load (AL) command to set the number of the macro for a vector. The LV
command is then used to transfer the low 8-bits of the accumulator to the vector table entry specified by
the LV command. If an interrupt is generated and that vector table entry has not been defined (equal to 0)
then the interrupt will not be executed. Note that this implies that macro "0" cannot be used as an interrupt
macro. If an interrupt is generated and it's vector table entry has been defined but the macro it specifies
has not, then an error will be reported.
2.2 Enabling and Disabling Interrupts
Loading a vector table entry will not enable an interrupt for operation. The Enable Vector
(EV) command must be used for this purpose. When the EV command is used, it will enable the interrupt
source (specified with the command) to function. In the event that it is necessary to disable an interrupt
source, there is a Disable Vector (DV) command that functions in a similar manner as the EV command.
In order to prevent multiple or continuous interrupts, as an interrupt is taken it is automatically
disabled. This means that the user must re-enable that interrupt using the EV command before it will
occur again.
2.3 Interrupt Sources
The following table lists all the possible interrupt sources.
Interrupt Source Level / Vector Interrupt Source Level/Vector
Axis 0 Error 31 Reserved 15
Axis 1 Error 30 Reserved 14
Reserved 29 Reserved 13
Reserved 28 Reserved 12
Axis 0 Fault 27 Reserved 11
Axis 1 Fault 26 Reserved 10
Reserved 25 Reserved 9
Reserved 24 Reserved 8
Axis 0 Limit 23 Reserved 7
Axis 1 Limit 22 Reserved 6
Reserved 21 Reserved 5
Reserved 20 Reserved 4
Axis 0 IP/IR 19 Digital Input 3 3
Axis 1 IP/IR 18 Digital Input 2 2
Reserved 17 Digital Input 1 1
Reserved 16 Digital Input 0 0
Table 5. Macro Interrupt Sources.
The Axis Error interrupts indicate that the position following error for a given axis has exceeded
the limit set by the Set Error (SE) command. Normally, when this limit is exceeded, the servo is disabled
and the "Error" bit in that axis' status word is set. If the interrupt for this condition is enabled, the
"Error" bit will still be set but the servo will not be disabled.

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The Axis Fault interrupts indicate that a fault condition (usually an over-temperature condition)
has arisen. Normally, when this condition is detected, the servo is disabled and the "Fault" bit in that axis'
status word is set. If the interrupt for this condition is enabled, the "Fault" bit will still be set but the
servo will not be disabled.
The Axis Limit interrupts indicate that either a Limit+ or Limit- condition for an axis has
been detected. Whether or not a limit input will be recognized is determined by the Limit On (LN)
and Limit Off (LF) commands. The action taken is determined by the Limit Mode (LM) command.
Digital Inputs 00 - 03 provide 4 levels of undedicated, user definable interrupts. The interrupt for a
given input will be active when that input is active.
2.4 Interrupt Priority
If more than one interrupt source becomes active at the same time, then the source with the
higher level will be executed first. Level/vector 31 has the highest priority and level/vector 0 has the
lowest priority.
2.5 Interrupt Completion
Once an interrupt macro (or set of macros) has finished executing, a Return from Call (RC)
command or an undefined macro may be used to cause a return from the interrupting macro back to the
interrupted macro where command execution will continue from where it was interrupted (see MS
command). In cases where it is undesirable to return to the interrupted macro, the Unpush Macro (UM)
command can be used to remove the previously pushed macro from the macro stack. This command can
also be used to completely reset the macro stack in order that the user program can be restarted.
2.6 Interrupt Latency
Interrupt sources are sampled before each command in a macro is executed. This means that the
amount of time that an interrupt is held off before execution (also known as interrupt latency) depends on
how long it takes the previous command to complete. For most commands this delay will be
imperceptible.
Commands such as Wait (WA), Wait for Edge (WE), Wait for Stop (WS), Wait for Off (WF), Wait
for On (WN) and Wait for Index (WI) would normally be a source of unacceptable delay in that they can
quite often be indeterminate in length. This problem has been avoided by making these instructions
interruptable. For example, if a WA10000 command (a 10 second delay) is currently in progress and an
interrupt comes along, the remaining delay period will be saved and then returned to after the interrupt
has completed. If the interrupt were to take 3 seconds to execute, then the total wait time of the WA10000
command would be extended to 13 seconds.
The Position Mode (PM), Torque Mode (QM), Velocity Mode (VM), Wait for Position Absolute
(WP) and Wait for Position Relative (WR) commands and any command that uses the serial
communications link are all commands that could cause unacceptable interrupt latency. Therefore, their
usage should be carefully considered where interrupts are possible.

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3. Entering Commands
Immediately after power-up, the LAC-26 is ready to accept commands. To verify this, you can hit
the ESC key. If everything is working properly, this should cause a greater than sign (">") prompt to
appear on your display. If not, you need to verify that the power and communications connections are
correct and verify the compatibility of the communications protocol.
Commands are entered via a "dumb" terminal or host computer such as a PC compatible.
Commands sent to the LAC-26 should consist of standard ASCII characters, and the command lines
should be followed by a carriage return. Linefeeds are not necessary since they are used for formatting
and therefore they are ignored. As characters are entered at the keyboard, they should be echoed on
your display. If your display echoes its own transmitted characters, you will want to issue the Echo Off
(EF) command; otherwise, the Echo On (EN) command (which is the default mode) should be issued. If
you enter an invalid command, the LAC-26 will respond with a question mark "?" followed by a code
indicating the type of error and the Status LED will begin to blink. These codes are listed in Appendix A,
LAC-26 Error Code Definitions.
If you make a mistake when entering a command, you can backspace to correct the error. If you
are entering commands and change your mind, hitting the ESC key will cancel the line and give a new ">"
prompt.
Once a command line has been entered and has finished executing, hitting the RETURN key
will cause the same command line to be re-executed. While a set of commands are executing, hitting
the space bar will cause command execution to pause until the space bar is hit again. Also, if the ESC
key is hit during execution or pause, command execution will be terminated, and you will receive a
new ">" prompt.
Command instructions are intended for use with the following syntax:
[Axis#]Command[Argument]<CR>
or...
[Axis#]Command[Argument],[Axis#]Command[Argument],...etc.
The axis number is normally specified as being from "1" to "2" with "0" being used to refer to both
axis' at the same time. Once an axis has been specified, the same one will remain in effect until another
is specified. For example, if the following were entered:
1SG100,SD500,SV1000000<CR>
or...
1SG100<CR>
SD500<CR>
SV1000000<CR>
the SG command specifies the axis number, so the subsequent SD and SV commands are performed on
the same axis. If the following command were issued:
0TP<CR>
it would have the same affect as issuing these commands:
1TP<CR>
2TP<CR>

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During interrupts and macro calls, the axis number is saved and then later restored. After an
interrupt macro entered or a macro call is taken, it is a good idea for the user to make sure an axis
number (if necessary) gets set during one of the first commands encountered.
The numerical range of an argument will vary depending on the command with which it is used.
The mathematical interpretation of the argument will depend on whether the Decimal Mode (DM) or
Hexadecimal Mode (HM) was the last issued (DM is the power on default). Both decimal and hexadecimal
numbers less than zero should be entered with a preceding minus "-" sign. If no argument is given, then it
will be assumed as "0". The exceptions to this are the Macro Define (MD), Macro Jump (MJ), Macro Call
(MC),Macro Sequence (MS), Reset Macro (RM) and Tell Macro (TM), commands. It should be noted that
commands can be strung together by using commas, up to a maximum line length of 127 characters.
If a command line is ended by a ";" and a comment, i.e...
>SG1000,SD5000 ; Set filter gains.<CR>
then the ";" and anything following it to the end of the line will be ignored. This feature is not particularly
useful if you are entering commands manually, as comments are not retained by the LAC-26. However, if
commands are downloaded to the LAC-26 from a host computer, the ability for line comments can make
program documentation possible and desirable.
3.1 Downloading Commands
In many cases, it is more convenient to enter commands using a text editor on a host computer
and then download that text file to the LAC-26 using a communications program such as ProComm or the
Microsoft Windows Terminal program. Whatever communications software is used, it must have the
ability to provide a short delay (approx. 100 mS) after transmitting each line to give the LAC-26 time to
interpret and store the commands that were just sent.
4. Introduction to Commands
The LAC-26 command instructions are varied and consist of several categories of purpose. The
command descriptions will be detailed by these categories.
4.1 Parameter Commands
The parameter setting commands are considered to be those for setting the operating conditions
of the servo system (i.e. PID filter gains, velocity, acceleration and etc.).
Command: aDBn -- Dead-Band --
Argument: 0 <= n <= 16383
Default: 0
This command sets the position following error dead-band for servo axis 'a'. The purpose for the
DB command is to allow an acceptable static position error for which there will be no restoring force. This
has the affect of reducing or eliminating "hunting" which is the continuous movement at or about a
position in trying to seek that position. This is useful for applications that cannot tolerate this condition.
Please note that the DB command is only in effect when the servo is not in motion (or when the Trajectory
Complete bit is set in the servo status word).
Related Commands: TF

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Command: aFAn -- Feed-forward, Acceleration --
Argument: 0 <= n <= 32767
Default: 0
This command allows for the adjustment of the PID digital filter acceleration feed-forward term for
servo axis 'a'.
During the course of a Position Mode (PM) or Velocity Mode (VM) move, at any point during
acceleration or deceleration (with a consistent load), the ideal required value of the servo output is fairly
consistent and somewhat predictable.
During acceleration or deceleration:
OUTPUT = (VELOCITY * FV_CONSTANT) + (ACCELERATION * FA_CONSTANT)
During constant velocity:
OUTPUT = (VELOCITY * FV_CONSTANT)
If this value can be dynamically predicted and summed with the output of the PID digital filter, in effect, it
reduces the burden of the PID filter to make lead/lag corrections based of the following error, thereby
enhancing performance.
Related Commands: FV, OM, OO
Command: FF -- Fail Input Off --
Default: Off
This command has no effect but is retained for backward compatibility purposes.
Command: FN -- Fail Input On --
Default: Off
This command has no effect but is retained for backward compatibility purposes.
Command: aFRn -- Set Derivative Sampling Period --
Argument: 0 <= n <= 127
Default: 0
This command allows for the adjustment of the derivative sampling interval for servo axis 'a'. The
period of this interval can be calculated by the following:
T = (n+1) * S * 0.000100
where "T" is the period in seconds, "n" is the FR command argument and "S" is the sample period count
specified by the Servo Speed (SS) command. For example, if the value previously set by the SS
command is 10 and the value set by the FR command is 1, then the derivative sample period will be:
(1+1) * 10 * 0.000100 = .002000 S or 2 mS
This command is useful in tuning the PID servo loop to the inertial properties of the system.
Related Commands: RI, SS

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Command: aFVn -- Feed-forward, Velocity --
Argument: 0 <= n <= 32767
Default: 0
This command allows for the adjustment of the PID digital filter velocity feed-forward term for
servo axis 'a'.
During the course of a Position Mode (PM) or Velocity Mode (VM) move, at any point along the
way (with a consistent load), the ideal required value of the servo output is fairly consistent and
somewhat predictable.
During acceleration or deceleration:
OUTPUT = (VELOCITY * FV_CONSTANT) + (ACCELERATION * FA_CONSTANT)
During constant velocity:
OUTPUT = (VELOCITY * FV_CONSTANT)
If this value can be dynamically predicted and summed with the output of the PID digital filter, in effect, it
reduces the burden of the PID filter to make lead/lag corrections based of the following error, thereby
enhancing performance.
Related Commands: FA, OM, OO
Command: aGRn -- Gear Ratio --
Argument: -8388607 <= n <= 8388607
Default: 0
This command sets the electronic gearing ratio for axis 'n'. A negative argument will cause a
direction reversal in the electronic gearing. The argument to this command is the desired gearing ratio
scaled by 65536.
Examples:
GR65536 ; Slave gear ratio is 1:1
GR131072 ; Slave gear ratio is 2:1
GR32768 ; Slave gear ratio is .5:1
GR6554 ; Slave gear ratio is .1:1 (actual gear ratio is
; .100006103516:1).
GR-65536 ; Slave ratio is 1:1 with direction reversal
Related Commands: EG
Command: aILn -- Set Integration Limit --
Argument: 0 <= n <= 16,383
Default: 0
This command clamps the level of influence that the PID digital filter integral term can use to
reduce the static position error of servo axis 'a'. When properly adjusted, this can enhance loop stability
and operation. The Integral Limit (IL) and Set Integral Gain (SI) must both be set to a non-zero value in
order for the integral term to have any effect.
Related Commands: SI

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Command: aLFn -- Limit Switch Input Off --
Argument: 0 <= n <= 3
Default: 0
This command disables one or more of the limit switch inputs for servo axis 'a'. The valid
arguments to this command determine which inputs will be disabled and are as follows:
n Limit Switch Inputs Disabled
0, 3 or no Limit+ and Limit-
argument
1 Limit+
2 Limit-
Related Commands: LM, LN
Command: aLMn -- Limit Switch Input Mode --
Argument: 0 <= n <= 3
Default: 0
This command is used to select how the LAC-26 will react when a limit switch is activated for
servo axis 'a'. The valid arguments for this command are as follows:
n Action
0 Turn servo off, continue commands
1 Stop abruptly, continue commands
2 Decelerate smoothly, continue
commands
3 Interrupt only
In all cases, the Error flag in the status word will be set. This will prevent the LAC-26 from moving
the servo until the flag is cleared by issuing the Motor On (MN) command. Before this command will have
any effect, the limit switch must be enabled with the Limit Switch On command (LN).
Related Commands: LF, LN
Command: aLNn -- Limit Switch Input On --
Argument: 0 <= n <= 3
This command is used to enable one or both of the limit switch inputs for servo axis ‘a’.
Once enabled, the servo will be stopped or turned off if a limit switch input goes active. At the
same time the Limit Switch Tripped and Error Flags will be set in the status word. These flags will
remain set until the servo is turned back on with the Motor On (MN) command. Once the servo is
turned back on, it can be moved out of the limit switch region with any of the standard motion
commands. The argument to this command determines which of the limit switch inputs will be
enabled. The coding is as follows:
n Limit Switch Inputs Enabled
0,3 or no argument Limit+ and Limit-
1 Limit+
2 Limit-
Related Commands: LF, LM

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Command: aOMn -- Output Mode --
Argument: 0 <= n <= 255
Default: 0
This command allows the user to determine what data gets sent to the D/A analog output
for a given axis. The upper four bits of the argument are for redirection of data and determine from
which axis the D/A channel will get it’s data. This allows both D/A channels to output data from the
same axis. If no redirection is specified, the default data used is that of the current axis.
Note: When outputting the servo output command, if no redirection is specified,
then the output
command as phase adjusted by the PH command will be output. If redirection is specified,
then the normalized data as reported by the TQ command will be output.
‘n’ Value Output
0 Servo Output Command
1 Servo Following Error ‘n+’ Redirect Channel
2 Servo Following Error * 64 0 Default
3 Variable USER1 16 1
4 Low Bits of Encoder Position 32 2
5 Reserved
6 Reserved
7 Reserved
Examples:
1OM0 ; Send axis 1 servo output command to D/A channel 1.
1OM16 ; Send axis 1 servo output command to D/A channel 1.
2OM0 ; Send axis 2 servo output command to D/A channel 2.
2OM32 ; Send axis 2 servo output command to D/A channel 2.
1OM0 ; Send axis 1 servo output command to D/A channel 1.
2OM17 ; Send axis 1 following error to D/A channel 2.
Command: aOOn -- Output Offset --
Argument: -32767 <= n <= 32767
Default: 0
This command allows the user to set a continuous output for servo axis ‘a’. In certain
applications, such as an overhanging load, there will be a continuous burden placed upon a servo axis. In
cases like these, where there is a predictable load, the OO command can be used to provide a
continuous restoring force that will be combined with the output of the PID digital filter. This has the affect
of improving the performance of the PID digital filter in that because it is not saturated with static load, it
has a better dynamic response to load disturbances.
Related Commands: FA, FV, OM

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Command: aPHn -- Set Servo Phasing --
Argument: 0 <= n <= 63
Default: 0
This command is used to set the output polarity, encoder phasing, Index input sense, Home input
sense, Limit+ and Limit- input sense for servo axis ‘a’. The polarity of the output will determine whether
the servo is driven in a direction that reduces or increases position error. The encoder phase will
determine whether the position count will increase or decrease for a valid encoder input sequence. The
Index sense determines what logic edge will cause the Index input to be active. The Limit+, Limit- and
Home sense determines whether these signals are active “on” or active “off.
To determine the argument to be used with the PH command, use the follow table and add the
required values together.
Add to 'n'
Output Phase Normal 0
Output Phase Reversed 1
Encoder Phase Normal 0
Encoder Phase Reversed 2
Index Active Level Low 0
Index Active Level High 4
Home Sense Active "ON" 0
Home Sense Active "OFF" 8
Limit+ Sense Active "ON" 0
Limit+ Sense Active 16
"OFF"
Limit- Sense Active "ON" 0
Limit- Sense Active "OFF" 32
For example, if it were necessary to reverse the encoder phasing and to set the Limit+ and Limit-
inputs to active "OFF", then 'n' would be (2 + 16 + 32) or 50. The default phasing and sense is equivalent
to issuing this command with a argument of 0.
Command: aRIn -- Sampling Rate of Integral --
Argument: 0 <= n <= 127
Default: 0
This command allows for the adjustment of the PID digital filter integral sampling interval for servo
axis 'a'. The period of this interval can be calculated by the following:
T = (n+1) * S * 0.000100
where "T" is the period in seconds, "n" is the RI command argument and "S" is the sample period count
specified by the Servo Speed (SS) command. For example, if the value previously set by the SS
command is 10 and the value set by the RI command is 1, then the integral sample period will be:
(1+1) * 10 * 0.000100 = .002000 S or 2 mS
This command is useful in tuning the PID servo loop to the inertial properties of the system.
Related Commands: FR

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Command: aSAn -- Set Acceleration --
Argument: 0 <= n < 1,073,741,823
Default: 0
This command sets the acceleration rate for servo axis 'a'. The 32 bit argument to this command
is scaled by 65536. This number determines how much the servo's velocity will be altered by each servo
loop interval (determined by the Servo Speed "SS" command) while it is accelerating or decelerating. If
this command is executed during a Position Mode move, it will be ignored.
Example:
Encoder: 500 lines or 2000 Counts/Rev
Desired Acceleration: 75 Rev/Sec2
Servo Loop Interval: 1,000 Hz
9830.4 = ((75 Rev/Sec * 2000 Counts/Rev) / 1000 Hz2) * 65536
To achieve an acceleration of 75 Rev/Sec2, the command SA9830 would be issued. A simpler
way to calculate the acceleration argument would be to determine a constant for your application by
which to calculate desired acceleration.
131.072 = K = ((1 Rev/Sec * 2000 Counts/Rev) / 1000 Hz2) * 65536
9830.4 = 75 Rev/Sec * K
Please note that if the Set Acceleration (SA) command is used with an argument of "0",
then you have commanded the velocity to change in steps of zero which means if the servo is
stopped it will not be able to move, and if the servo is moving it will not be able to change velocity.
Related Commands: SS, SV
Command: aSCn -- Set Current Mode Gain --
Argument: 0 <= n <= 32,767
Default: 0
This command sets the "current mode" gain for servo axis 'a' used by Torque Mode (QM1
only, see QM command). This allows the response of the current error integrator to be adjusted to suit a
given application. A low SC value will provide slow response to load changes while a high SC value will
provide quick response to load changes. If SC is set is too low then inadequate control may occur. If the
SC setting is too high then the system may be unstable. A good "general" value for SC is about 8000.
Related Commands: QM, SQ
Command: aSDn -- Set Derivative Gain --
Argument: 0 <= n <= 32,767
Default: 0
This command sets the derivative gain term of the PID digital filter loop for servo axis 'a'.
Related Commands: SG, SI, IL