Rockwell Automation 1771-QA Stepper Positioning Assembly User Manual User Manual
Page 36
3–14
Programming and Operation
Publication 1771-UM002A–EN–P – May 2000
Figure 3.9
Offset and Preset Words
17
10 07
00
0
1
7
0
Data Table
9
9
9
9
9
9
9
9
9
0
1
0
0
0
0
0
0
MCW
Offset
MS Preset
LS Preset
0 = Add
1 = Subtract
1 = Assert
Initialization
Preset
0 = Move
Preset
10522
The moves affected by the offset will be those stored in the working
and storage moveset when the command is received. If additional
movesets have been programmed, the offset command must be
re-enabled when additional movesets are transferred to the stepper
controller module.
Preset Word
The preset word can store values that serve two functions. One
function, initialization preset, is used by the stepper controller
module to define the starting point value of the positioning profile.
The other function, move preset, can be used to extend one or more
moves of the profile beyond the 999,999 pulse (position) limit of the
stepper controller module. In either case, the preset word can be
loaded with the necessary value, the function enabled and another
value loaded as needed. When used, the preset value becomes the
new position reference of the profile.
The preset can be any value between 0 and 999,999. Preset data is
contained in two words, one for the most significant (MS) 3 digits,
the other for the least significant (LS) 3 digits (Figure 3.9). Preset
values are entered in BCD in bits 00-13. Bits 14-17 in the LS preset
word and bits 14-16 in the MS preset word are undefined and must
be loaded with zeros. Bit 17 of the MS preset word is the assert bit
for the initialization preset.