Function mode
Original instructions
About us
ERT data transfer
The number of I/O words available on the S908 remote drops is limited to 64 inputs and 64 outputs. For this reason, the number of settable ERT modules per remote drop with the currently selected minimum requirements of 8 input words and 5 output words is limited to 8. There is no quantity limitation of ERT modules in EIO drops.
The size of the required ERT data transfer is considerably larger:
These inconsistent size requirements necessitate the use of a special transfer EFB called ERT_854_20 to execute the required operations on the PLC and to adjust the ERT representation of the data in Multiplex form. This type of EFB is required for every ERT module.
To simplify matters, configure only the EFB parameters which will actually be used. This saves on configuration, particularly when the counter inputs and event inputs get mixed with one another. Memory is not saved because Control Expert fills the outputs with invisible.
Underlying structure of the register block
Underlying structure of the ERT_854_20 input register block with 8 %IW input words for transfer from the ERT to the PLC:
Contents
Function
Digital inputs 1...16
Digitally processed input data which is cyclically updated (the module’s input address corresponds to that of the digital standard input modules, that is inputs 1...16 correspond to bits 15...0)
Digital inputs 17...32
Transfer status
IN transfer status (TS_IN)
MUX 1
Multiplex data block for block transfer, such as:
  • 1 event with 5 byte time marker or
  • 2 counter values of maximal configuration 32 or
  • 1 status word
MUX 2
MUX 3
MUX 4
RESERVED
Reserved for internal use
Simplified structure of the ERT_854_20 output register block with 5 %MW output words for the transfer from the PLC to the ERT.
ERT_854_20 output register block:
Contents
Function
Transfer status
OUT transfer status (TS_OUT)
MUX 1
Time data block for the ERT for the clock synchronization
MUX 2
MUX 3
MUX 4
NOTE: User interfaces are normally the inputs and outputs of the ERT_854_20 EFB, not the %IW and %MW input/output words.