GE Industrial Solutions HE300GEN251 - Manual (Page 10)

CH. 2: DRIVE OVERVIEW 23 SEP 1999 PAGE 11
CHAPTER 2: DRIVE OVERVIEW
2.1 General
It is important to have a basic understanding of how the AV-300i Drive interacts with the Genius Serial
Bus Interface (SBI) such as the GEN250/251.
2.2 Two Versions of SBI Cards Available / Using an Additional Option (DGF Card)
There are two versions of the SBI card - the internally mounted GEN250 and the externally mounted
GEN251.
Note that there instances when the user needs to use both an SBI card as well as a separate option
called a DGF card. Only one option card (either the GEN250 internal SBI card or the DGF card) can be
installed within the drive. If the application requires
both an SBI card and a DGF card, the DGF card
must be mounted internal to the drive. In this case, the GEN251 SBI card must be mounted external to
the drive. If the application does not require a DGF card, either the GEN250 SBI card or the GEN251
SBI card can be used.
The SBI provides a communications path between itself and the drive. The SBI can access any
predefined parameter within the AV-300i drive. Reference the AV-300i instruction manual for a
description of each of the available drive parameters.
2.3 High and Low Priority Communication Channels
The SBI provides two communications channels to and from the drive, high priority and low priority. A
maximum of 16 directed control word parameters and 32 global data word parameters are allowed. Of
these, up to 6 can be assigned to the high priority channel. The balance must be assigned to the to the
low priority channel. All parameters assigned to the high priority channel are exchanged with the drive
every 2 milliseconds. The drive can also pack/unpack up to 16 high priority bit parameters into/from a
single high priority word parameter. If this feature is used, 5 high priority word parameters and 16 high
priority bit parameters can be processed. Due to the relatively small number of parameters available in
the high priority channel, these parameters should be reserved for the most critical parameters.
To access each low priority parameter, the SBI must poll the drive one parameter at a time. This process
is very time consuming. A minimum of 100 milliseconds is required to access each drive parameter. The
SBI can also pack/unpack up to 16 low priority bit parameters into/from a single low priority word
parameter.