ProSoft Technology MVI56-BSAPS - Manual (Page 61)

Reference MVI56-BSAPS ♦ ControlLogix Platform
Bristol Babcock Serial Slave Module
ProSoft Technology, Inc. Page 61 of 83
September 22, 2008
Normal Data Transfer
Normal data transfer includes the paging of the user data found in the module's
internal database in registers 0 to 2740 and the status data. These data are
transferred through read blocks (input image). Write blocks (output image)
transfer data into module's internal database in register 3000 to 5740. These
data are gathered in a response command to a master. The Module Setup
section provides a description of the data objects used with the blocks and the
ladder logic required. The structure and function of each block is described in the
following topics.
Read Block
These blocks of data transfer information from the module to the ControlLogix
processor. The structure of the input image used to transfer this data is shown in
the following table.
Offset Description Length
0 Reserved 1
1 Write Block ID 1
2 to 201 Read Data 200
202 Program Scan Counter 1
203 to 204 Product Code 2
205 to 206 Product Version 2
207 to 208 Operating System 2
209 to 210 Run Number 2
211 to 214 Port 1 Error Status 4
215 to 218 Port 2 Error Status 4
219 to 224 Data Transfer Status 6
225 Port 1 Current Error/Index 1
226 Port 1 Last Error/Index 1
227 Port 2 Current Error/Index 1
228 Port 2 Last Error/Index 1
229 to 248 Spare 20
249 Read Block ID 1
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 is as follows:
R1W1 → R2W2 → R3W1 → R1W2 → R2W1 → R3W2 → R1W1