ProSoft Technology MVI69-ADM - Manual (Page 50)

Understanding the MVI-ADM API MVI-ADM ♦ 'C' Programmable
Developer's Guide 'C' Programmable Application Development Module
Page 50 of 342 ProSoft Technology, Inc.
February 20, 2013
Data Transfer
Data is transferred over the backplane using the module’s input and output
images. The module is configured with an eight-word input image and a seven-
word output image. The module and the Flex processor use these images to
page data and commands. The input image is set (written) by the module and is
read by the Flex processor. The output image is set (written) by the Flex
processor and read by the module. The following illustration shows this
relationship.
The module’s program is responsible for setting the block identification code
used to identify the data block written and the block identification code of the
block it wants to read from the processor. User configuration information
determines the read (Read Start Register) and write (Write Start Register)
locations in the database and the amount of data transferred (Read Register
Count and Write Register Count).
Each read and write operation transfers a six-word data area. The write operation
contains a two-word header that defines the block identification code of the write
data and the block identification code of the read block requested. These
identification codes are in the range of 0 to 666. A value of zero indicates that the
block contains no data and should be ignored. The first valid block identification
code is one and refers to the first block of six words to be read or written.