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MPC-325 SERIES OPERATION MANUAL – REV. 3.20F (20200303)
1. Task-Complete Indicator: All commands will send back to the computer the “Task-
Complete Indicator” to signal the command and its associated function in controller is
complete. The indicator consists of one (1) byte containing a value of 13 decimal (0D
hexadecimal), and which represents an ASCII CR (Carriage Return).
2. Intercommand Delay: A short delay (usually around 2 ms) is recommended between
commands (after sending a command sequence and before sending the next command).
3. Clearing Send/Receive Buffers: Clearing (purging) the transmit and receive buffers of the
I/O port immediately before sending any command is recommended.
4. Positions in Microsteps: All positions sent to and received from the controller are in
microsteps (µsteps). See
Microns/-microsteps conversion
table) for conversion between
µsteps and microns (micrometers (µm)).
5. Ranges and Bounds: See
Ranges and Bounds
table for exact minimum and maximum
values for each axis of each compatible device that can be connected. All move commands
must include positive values only for positions – negative positions must never be
specified. All positions are absolute as measured from the physical beginning of travel of a
device’s axis. In application programming, it is important that positional values be
checked (>= 0 and <= max.) to ensure that a negative absolute position is never sent to
the controller and that end of travel is not exceeded. All computational relative positioning
must always resolve to accurate absolute positions.
6. Absolute Positioning System Origin: The Origin is set to a physical position of travel to
define absolute position 0. The physical Origin position is fixed at beginning of travel
(BOT). This means that all higher positions (towards end of travel (EOT)) are positive
values; there are no lower positions and therefore no negative values are allowed.
7. Absolute vs. Relative Positioning: Current position (‘c’) and move commands always use
absolute positions. All positions can be considered “relative” to the Origin (Position 0), but
all are in fact absolute positions. Any position that’s considered to be “relative” to the
current position, whatever that might be, can be handled synthetically by external
programming. However, care should be taken to ensure that all relative positions are
accurately translated to correct absolute positions before initiating a move command.
8. Position Value Typing: All positions sent and received to and from the controller are in
microsteps and consist of 32-bit integer values (four contiguous bytes). Position values can
be either positive or negative, so type must be “signed”. Although each positional value is
transmitted to, or received from, the controller as a sequence of four (4) contiguous bytes,
for computer application computational and storage purposes each should be typed as a
signed integer (“long” or “signed long” in C/C++; “I32” in LabVIEW, etc.). Note that in
Python, incorporating the optional NumPy package brings robust data typing like that
used in C/C++ to your program, simplifying coding and adding positioning accuracy to
the application.
9. Position Value Bit Ordering: All 32-bit position values transmitted to, and received from,
the controller must be bit/byte-ordered in “Little Endian” format. This means that the
least significant bit/byte is last (last to send and last to receive). Byte-order reversal may
be required on some platforms. Microsoft Windows, Intel-based Apple Macintosh systems
running Mac OS X, and most Intel/AMD processor-based Linux distributions handle byte
storage in Little-Endian byte order so byte reordering is not necessary before converting
to/from 32-bit “long” values. LabVIEW always handles “byte strings” in “Big Endian”
byte order irrespective of operating system and CPU, requiring that the four bytes
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