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CUSTOMER SUPPLIED THUMBWHEEL INTERFACE
Introduction
The thumbwheel interface provides the user with a non-serial interface method for making
changes to specific motion functions. The user can set up the thumbwheel to change velocities
(in RPM only), distances/positions, dwell times, index counts and acceleration and deceleration
times. As many as 20 external BCD characters can be read into the digital drive. Once read,
these characters are stored in an internal character buffer. The actual buffer has a capacity for 32
characters to support other parallel interfaces. When customer thumbwheels are used, the 20
possible thumbwheels are read into the first 20 locations of the character buffer designated as (0-
19).
Figure 28
Character Buffer
The character buffer contents can be pre-programmed via serial commands to represent distance,
velocity (in RPM only), count, etc. This mode of operations has 8 lines dedicated to transfer data
and 10 lines dedicated to selection of data pairs.
Since 8 lines of data are provided and each BCD digit requires 4 lines, thumbwheel digits are
read two at a time. The 10 select lines allow the use of up to 10 pairs of digits (20 thumbwheel
digits). Once the thumbwheel data is set activating the (EXECUTE) input transfers the new data
to its respective function and it becomes the active data.
An output called (ERROR) is provided as a means for the drive to tell an external device that
data is out of range.
The inputs and outputs from this parallel interface are not typically isolated and are relatively
low voltage (15 VDC). Care must be taken to assure that electrical noise does not enter the
digital drive by a careless wiring implementation of this interface. In general, the wiring should
be kept short (5 to 20 feet). The wiring should be shielded with the shield connected at pin 37 of
the parallel interface connector. The wiring cannot be run adjacent to any high voltage wiring.
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