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Auxiliary Drive to ISBus Interface Board IS200ADII GEI-100305
4
Performance
On the ISBus, the controller sends control bits and references for each drive in a
single stream of bytes. The first drive wired to the controller receives the stream of
bytes, retrieves its command bits and references, and passes the stream of bytes onto
the next drive substituting its feedback bits and variables for the command bits and
references. When the controller receives the stream of bytes from the bus, it is
receiving the feedback bits and feedback variables from the drives.
The ISBus scan time can be selected to be 1, 2, 4, or 8 ms. These times are limited to
the number of devices on the bus. See Table 2 for performance factor descriptions.
Table 2. Performance Factors
Performance
Factor Description
Control logic
sweep rate
Time required for a sweep of the control logic being executed in the
controller (typically measured in ms).
Configured frame
time of the ISBus
1, 2, 4, or 8 milliseconds (Set by the master).
Types of devices
on the bus
The contribution of each device to the bus sweep rate varies with the
quantity of I/O data being exchanged with the controller. Each AcDc2000
drive contributes about 0.20 ms (200 µs). This data is used in calculating
what the frame time should be.
Quantity of
devices on the bus
As the number of devices on the bus grows, so does the bus sweep rate.
This data is used in calculating what the frame time should be.
AC/DC2000 LCP
to DCP
LCP will pass the reference bits and references to the drive control
processor (DCP) in one ms time with an average of 500 µs.
AD/DC2000 DCP
Algorithms
Many of the references are passed to the DCP in generic setpoint
variables. These variables are read by the DCP at different update times
(11, 22, or 44 ms).
AD/DC2000 DCP
Algorithms
Many of the feedbacks are passed from the DCP in generic feedback
variables. These variables are written by the DCP at different update
times (11 ms, 22 ms, 44 ms).
LCP to ISBus LCP obtains drive feedbacks from the LCP/DCP dual-port RAM at the
end of a frame and loads these feedbacks into the controller. These
feedbacks are sent to the master in the next ISBus frame.