Rockwell Automation 1771-QC , D17716.5.25 SER/B SERVO POS - Manual (Page 26)

Positioning with Allen-Bradley PC
Chapter 4
4Ć2
positioning assembly through the I/O scan. The PC processor acts on a
block transfer read instruction to receive status blocks. Based on the
status information received, the PC processor acts on a block transfer
write instruction to send either parameter blocks, move blocks, or control
blocks.
Figure 4.2
Where the Servo Positioning Assembly Fits in a PC System
PC
Processor
Servo
Positioning
Assembly
Output Scan
Parameter, Moveset, and Command Blocks
Input Scan
Status Blocks
Outputs
Inputs
12006
Although the servo positioning assembly sends data to and receives data
from the data table through the I/O scan, the positioning loop is closed on
the 1771-ES expander (at the positioning loop summing point). This
allows the 1771-ES expander to provide a servo sample period of 2.4ms,
independent of I/O scan.
You must describe the axis motion you want in moveset blocks in the data
table. You can enter a maximum of 21 separate move blocks in a moveset
block (Figure 4.3).
Independent of I/O Scan
Move/Moveset