ABB AC 31 - 5.3.3. Utilization of the function blocks

Program Optimization
ABB Control - AC 31 Page 6-17
1SBC 260400 R1001-b 06.99
5.3.3. Utilization of the function blocks
Use of the function blocks simplifies the communication between the master/slave central units
and enables a large exchange of data.
The data exchange takes place from the master to the slave as well as from the slave to the
master.
A data zone may thereby be transmitted from one central unit to another.
The exchange of a complete data table is totally transparent for the user.
The slave central unit should be configured for CS 31 bus communication, 8 words on
emission and 8 words on reception.
The exchange of words is effectuated 7 words by 7 words at the most , the 8
th
word being
reserved for the handshake which controls the dataflow.
A total of 4 function blocks is required for a transfer from one central unit to another.
The following function blocks are available:
- for the master : MT_CS31 (data transmission to the slave)
MR_CS31 (data reception from the slave)
- for the slave : ST_CS31 (data transmission to the master)
SR_CS31 (data reception from the master)
The MT_CS31(master) and SR_CS31(slave) function blocks are used for a data transfer from
the master central unit to the slave central unit (see Figure 6-11).
DATA
OWxx.07
OWxx.01
DATA
IW00.07
IW00.01
SR_CS31MT_CS31
OW xx.00
IW xx.07
IW 00.00
OW00.07
Handshake
Figure 6-11 : Data transfer from master to slave
The following information is necessary for these blocks:
- Slave number.
- The number of words to use per exchange : a data table may be transmitted over the CS 31
bus 7 words by 7 words or, 6 words by 6 words or, 5 words by 5 words, etc. It is therefore
possible to use the unused words for a rapid data transfer between central units at each CS 31
bus cycle. The data transfer may therefore be carried out with 2 different time bases. A typical
application is the transfer of parameters from the CS 31 master to the slave 4 words by 4
words, the 3 remaining words being reserved for the rapid transfer of the inputs/outputs. The
available outputs on the master are OWxx.07, OWxx.06, etc. and the corresponding inputs on
the slave are IW00.07, IW00.06, etc. This number should be identical for both functions.