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Reference MVI56-CAS ♦ ControlLogix Platform
Teledyne CA Slave Module
ProSoft Technology, Inc. Page 53 of 86
December 26, 2007
The Read Block ID is an index value used to determine the location of where the
data will be placed in the ControlLogix processor controller tag array of module
read data. Each transfer can move up to 200 words (block offsets 2 to 201) of
data. In addition to moving user data, the block also contains status data for the
module. This last set of data is transferred with each new block of data and is
used for high-speed data movement.
The Write Block ID associated with the block requests data from the ControlLogix
processor. Under normal, program operation, the module sequentially sends
read blocks and requests write blocks. For example, if three read and two write
blocks are used with the application, the sequence will be as follows:
R1W1 R2W2 R3W1 R1W2 R2W1 R3W2 R1W1
This sequence will continue until interrupted by other write block numbers sent by
the controller or by a command request from a node on the TCA network or
operator control through the module's Configuration/Debug port.
Write Block
These blocks of data transfer information from the ControlLogix processor to the
module. The structure of the output image used to transfer this data is shown in
the following table:
Offset Description Length
0 Write Block ID 1
1 to 200 Write Data 200
201 to 206 Time Data 6
207 to 247 Spare 41
The Write Block ID is an index value used to determine the location in the
module's database where the data will be placed. Each transfer can move up to
200 words (block offsets 1 to 200) of data.
5.2.3 Configuration Data Transfer
When the module performs a restart operation, it will request configuration
information from the ControlLogix processor. This data is transferred to the
module in specially formatted write blocks (output image). The module will poll for
each block by setting the required write block number in a read block (input
image). Refer to the
Module Set Up
section for a description of the data objects
used with the blocks and the ladder logic required. The format of the blocks for
configuration is given in the following topics.