Manual

1-2 Introduction
Input Buffer
As they are received, ACL commands are put into a 256-byte input buffer. After the
machine finishes processing one command, it fetches the next from the buffer. In order to
prevent the host from sending characters too fast and thus overflowing the buffer, one of
four input buffer handshakes must be implemented within the host. These are: Hardwired
DTR, Xon/Xoff, Enq/Ack, and Software Checking. The host sets up the desired handshake
by sending escape sequences to the Automove System. For more information about
handshakes, which handshake to use, and how to set up a handshake, see Chapter 5 RS-232C
Communications, Chapter 6 Escape Sequences, and Appendix F Choosing a Handshake.
Numeric Coordinate Systems
The Automove X-Y tables have a carriage which moves above a flat surface called a platen.
If you are using the stand-alone controller with your own mechanical system, your physical
system may not have anything resembling a carriage or platen. However, for convenience in
this document we talk about moving the carriage above the platen.
The physical coordinate system is based on physical motor counts, or microsteps, which for
the Automove X-Y tables are nominally 0.001 inch. Calibration factors can be entered via
the CF command (see Chapter 3) so that the host software can work in true 0.001 inch
Calibrated Units or any other convenient units. At power up the System designates the
current position to be the Home position, or (0,0) microsteps.
The FH ("Find Home Switches") command causes the carriage to move to the lower-left
corner of the platen. The point where both Home switches have closed is then defined to be
the Home position, or (0,0) microsteps. Another way to find the Home switches is by a
front-panel manual re-reference sequence; see Chapter 4. Typically, an FH command or
manual re-reference should occur before any ACL motion commands or other front panel
interactions are attempted. If the Home switches are not found, the Automove System will
not "know" where the carriage is with respect to the physical boundaries, and the TL travel
limits will not work correctly. Also, since vectors and arcs to negative physical coordinates
are prohibited, a portion of the platen would only be reachable via the Arrow buttons.
The origin of the Calibrated Units coordinate system (the "Origin position") can be offset
from the Home position via the front-panel SET ORIGIN button, the SO command, or the
BP command. Also, the BP command can cause the entire coordinate system to be rotated
by a specified angle.
See the BP, CF, CR, MA, and SO commands in Chapter 3 for more information about
calibration factors, origin offsetting, pattern rotation, and linearity correction.
Within this document the term Calibrated Units always refers to this "corrected" coordinate
system. The term microsteps always refers to an actual number of physical microsteps at
the motors. If you want your computer program to deal in units other than microsteps, the
calibration factors can be changed to suit your needs. For example, values near 1.0000 can
be used to compensate for small mechanical variations, or larger values can be used so that a
Calibrated Unit is one inch or one millimeter. (This does not change the physical size of a
microstep, only the number of microsteps per calibrated unit.) Use caution, though, since
the calibration factors affect vectors but not the shape of arcs.