Use the stt subroutine status word – Rockwell Automation 1770,D17706.5.21 SMART TRANSMITTER TOOLKI User Manual

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Chapter 3

Using The Smart Tranmsitter Toolkit

3-4

The STT subroutine status word handshakes with your PLC ladder logic.
The STT subroutine status word:

tells you when the STT subroutine is entered and exited
tells you when the STT subroutine is enabled and done
lets you trigger the STT subroutine
tells you when the STT subroutine errors

The STT status word is integer word 30 of the integer file that is passed in
with your JSR instruction. This table shows the bits that are used in the
STT subroutine status word.

STT Subroutine Status Word 30

Bit 0

STT Enter/Exit Bit

Use bit 0 to debug your program. When called, the STT subroutine sets bit 0 to 1. When

the STT subroutine exits, the subroutine sets bit 0 to 0. This lets you know when the STT

subroutine is entered and exited.

Bit 1
Bit 2

STT Enable Bit
STT Done Bit

Bit 1 indicates that the STT subroutine is in the middle of processing a HART command.
Bit 2 indicates that the STT subroutine is done processing a command.
When you make an unconditional call to the STT subroutine, if the subroutine is not

already enabled, it sets bit 1 to 1 and bit 2 to 0. When the STT subroutine is done

processing a Hart command (successful or not), it sets bit 2 to 1 and bit 1 to 0. When bit

2 is set to 1, you can process the output data that is returned by the STT subroutine.

Bit 3

STT Trigger Bit

Bit 3 is the STT subroutine trigger bit. Use bit 3 to tell the STT subroutine to process the

requested command. Even though you call the STT subroutine with an unconditional

JSR, it does not process the HART command unless bit 3 is set to 1. When the STT

subroutine sees bit 3 set to 1, it processes the request. When the request is first

detected, the STT subroutine is enabled and it sets bit 3 to 0.

Bit 4

STT Error Bit

Bit 4 is the STT subroutine error bit. This bit is set if either the BTW or the BTR has

failed. Any data, except words 30 and 31, in the output area is invalid if this bit is set.

Bits 5Ć7

Reserved

Reserved for future use.

Bit 8

STT BTW Retry Bit Bit 8 indicates that the BTW has returned an error and is being retried by the STT

subroutine.

Bit 9

STT BTR Retry Bit Bit 9 indicates that the BTR has returned an error and is being retried by the STT

subroutine.

Bits 10Ć15

Reserved

Reserved for future use.

Example

In this example, the STT trigger bit is set to 1 if the STT enable bit is set to 0.

N10:60

3. Use The STT Subroutine

Status Word