Input vs. Output vs. InOut vs. Static vs. Temp

[TurpoUrpo]

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Back in the dark ages ( 1980's ) TI had the concept of DMA. Our TI controller could work with TI505 PLCs with no code. Commands could be issued from DOS based software and the status monitored but all could be done with no PLC code. 30 years later there is no improvement. Shame on all. The PLC world is moving backward not forward. Try making a Siemens or Rockwell controller work without PLC code.

What it should do without code? put some strobo in outputs? Is not PLC's job to run code?

 

[PeterW]

Back in the dark ages ( 1980's ) TI had the concept of DMA. Our TI controller could work with TI505 PLCs with no code. Commands could be issued from DOS based software and the status monitored but all could be done with no PLC code. 30 years later there is no improvement. Shame on all. The PLC world is moving backward not forward. Try making a Siemens or Rockwell controller work without PLC code.

You might think its a backward step that PLC's cannot be empty and processing code, I think all maintenance personal would disagree.

The trouble I see with computer grads programming PLC's is the fact they don't understand what a PLC is and why it is there and then make everything about 1000 times more complex than it should be by trying to emulate a C++ program.

 

[Peter Nachtwey]

Our controllers on the old TI505 had 8 registers that were used as address registers to point to places in Vmem where the status area, command area, 4 parameter areas are, a step or sequencer table and a checksum. This could be done using TISOFT directly. When the checksum was correct the controller would automatically read and write to these areas automagically. No ladder required. An HMI could then read the status are to display. Commands could also be download directly to the command area and the motion controller would execute it. No ladder required. Again, try that with any modern PLC system. The SLC/500 and 1746-QS isn't quite as slick ( pun intended ). If there was an easy way to access the M-memory from RS500 it would have been good.

You might think its a backward step that PLC's cannot be empty and processing code, I think all maintenance personal would disagree.

How can you argue with simplicity? The people that used it loved it.

The trouble I see with computer grads programming PLC's is the fact they don't understand what a PLC is and why it is there and then make everything about 1000 times more complex than it should be by trying to emulate a C++ program.

What difference does it make? They learn fast enough once they get over the shock that PLCs are crippled compared a real computer. Try writing a quick sort in ladder.