Host Communications - National Instruments PCI-7342 User Manual

Note Once mapped to an axis, all features and functions of a resource are available as part
of the axis. It is not necessary to remember or use the resource number directly when
accessing these features. Resources are referenced by axis number once assigned to that axis.

Host Communications

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If an encoder resource is not needed for axis control, you can use it for any
number of other functions, including position or velocity monitoring, as a
digital potentiometer encoder input, or as a master encoder input for
master/slave (electronic gearing) applications.
Each axis also has an associated forward and reverse limit input, a home
input, a high-speed capture trigger input, a breakpoint output, and an inhibit
output. These signals can be used for general-purpose digital I/O when not
being used for their motion-specific purpose.
The host computer communicates with the controller through a number of
memory port addresses on the host bus.
The primary bi-directional data transfer port is at the base address of the
controller. This port supports FIFO data passing in both send and readback
directions. The PCI-7342 controller has both a command buffer for
incoming commands and a return data buffer (RDB) for readback data.
Two read-only status registers are at offsets from the base address.
The communications status register (CSR) provides bits for
communications handshaking as well as real-time error reporting and
general status feedback to the host PC. The move complete status (MCS)
register provides instantaneous motion status of all axes.
4-5
Chapter 4 Functional Overview
NI PCI-7342 Hardware User Manual