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How to automatically reset a control bit in a SCADAPack using TelePACE Studio.

An HMI, SCADAHost or master PLC may want to write to a SCADAPack coil via ModBUS to request some specific operation.

A SCADAPack running with TelePACE does not have a standard Set/Reset bit ability that might be seen in other controllers and programming environmnets but there is a way to implement this functionality using the PUTB function.

The PUTB function operates on 16-bit words. This can either be 4xxxx holding registers or 0xxxx coil registers. Begin coil blocks at the start of a 16-bit word within the controller memory. Suitable registers are 00001, 00017, 00033, etc...
The index corresponds to the position within the 16-bit word. A bit index of 0 is the most significant bit of the destination block. A bit index of 15 corresponds to the least significant bit (the lowest coil number).
 

In the example below, an HMI will do a ModBUS write to either coil 00161 or 00162 to initiate some sort of operation. 


For either 00161 or 00162, their respective timer will reset after ten seconds and trigger a PUTB function. In this example, the PUTB functions are operating on the coil block of registers 00161-00176 (but only specifically targetting 00161 and 00162). The PUTB function will then put a zero (the middle input is not energized) into the bit being indexed. 
In this example, coil 00161 is the least significant bit within the coil block and will require the index value of 15.Coil 00162 corresponds to an index value of 14.

For complete details about the PUTB function, please see the TelePACE Studio User and Reference Manual.
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