ProSoft Technology MVI56-AFC - Manual (Page 201)

MVI56-AFC ♦ ControlLogix Platform MVI56-AFC Backplane Communication
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 201 of 316
February 25, 2011
Use the "ignore output" bit of the block ID to control the scheduling of master
mode transactions and the "skip input" bit to control the retrieval of the result.
The output block is processed and a master transaction scheduled when "ignore
output" is clear and there is no transaction currently pending; in all other cases
the output is ignored. While "skip input" is clear, a pending transaction is
indicated by the "pending" bit, if no transaction is pending then the results of the
latest transaction are returned, and in all cases the "transaction number" of the
latest or current transaction is returned.
Modbus Master OFB Modbus Master IFB
Element Attribute Element Attribute
0 Block ID - Function Code &
Length.
0 Block ID - Function Code &
Length
1 Transaction Number 1 Transaction Number Echo
2 Data Item Size & Swap Options
(see below)
2 Error Code (see below)
3 Slave Address 3 Data Read Element 1 (if used)
4 Modbus Register Address 4 Data Read Element 2 (if used)
5 Number of Data Items 5 Data Read Element 3 (if used)
6 Data Write Element 1 (if used) 6 Data Read Element 4 (if used)
… …………………………………. … ………………………………….
… …………………………………. … …………………………………..
Data Item Size and Swap Options
The data item size is given by one of the following values:
0 - Bit (In the AFC, packed 16 to a word)
1 - Word (16-bit registers)
2 - long (32-bit items as register pairs)
3 - long remote (32-bit items as single registers)
To configure byte or word swapping, add 10 for byte swap (except size 0) and/or
add 20 for word swap (sizes 2 and 3 only).