BTW, BTR instruction

[Amy_Fields]

Could someone explain why and how one would is the BTW/BTR instruction in RsLogix 500?

Thank you

 

[The Plc Kid]

RIO Remote Io is an example where you have a remote chasis of IO you want to control over RIO you would use BTR and BTW instructions to read and write data to that rack.

It can be used to exchange data with Panelview and drives also.

 

[daba]

The "standard" and "default" data exchange between your processor and I/O modules is just a single word of data, enough to accommodate 16 digital inputs, or outputs.

So the RIO protocol basically was designed from the word go to only transfer single words of data between the processor and the I/O modules.

As the technology evolved, modules like analog I/O, for example, which have data for multiple channels, need more than a single word of data to allow them to be used, so the BTW/BTR functionality was integrated into RIO to allow a single module to receive and send more than 1 word of data.

BTW/BTR is not needed for standard analog I/O modules in Logix500, because the multiple word transfer between the processor and analog I/O modules has been "built-in" to the RIO protocol. It most certainly is needed for analog I/O modules in Logix5.

Just think of BTW and BTR as Messages to/from the module, that are transferred on the RIO network when a module (or HMI) needs more than a single word of data.

The Block Transfer capability allows for (up to) a 64-word data exchange with a module, either read or write, and has to be initiated in ladder code with BTW and BTR instructions.