How to Disable and Re-Enable AutoTune


This document outlines the process to disable and re-enable AutoTune using ItemTest. By default, Monza 6 and Impinj M700 chips will have AutoTune enabled. The instructions here use a Monza R6 tag and ItemTest but this process also works for Impinj M730, M750, Monza R6-A, Monza R6-B, and Monza R6-P tag chips, noting that the AutoTune disable bit is in a different location. Any RAIN RFID reader that can read and write to reserved memory can follow the steps outlined here to disable or re-enable AutoTune.

Hardware Required

  • Windows host PC
  • Speedway Revolution with a Mini-Guardrail antenna, connected via Ethernet to the computer
  • Monza R6 tag or other Impinj tag with AutoTune (Impinj M730/M750, Monza R6-A/B/P)

Software Required

AutoTune Disable Bit Location

The AutoTune disable bit is marked "A" on the memory map below, in word 5 of the reserved memory for Monza R6. When A is set to 0, AutoTune is enabled. When set to 1, AutoTune is disabled. To set this bit to one and disable AutoTune, send a write command to that word greater than or equal to 8000h, such as FFFFh. (Note that "8000" in hex is the same as "1000 0000 0000 0000" in binary.) Only bit A will be written to. This word may now be inventoried to verify that bit A has changed. To re-enable AutoTune, send a write command of less than or equal to 7FFFh, such as 0000h. This will effectively set A to 0.

Figure 1. Reserved memory map of Monza R6, taken from section 4.1 of the Monza R6 TagChip Datasheet


Note: The AutoTune disable bit is in word 4 of reserved memory for Impinj M730/M750, Monza R6-A, Monza R6-B, and Monza R6-P. When writing to this word for these tag chips, writing a value of 0001h will disable AutoTune and a value of 0000h will enable AutoTune. Writing to this work will also write the short range bit, S, and the memory map selection bit, M, (Monza R6-P only), but writing 0001h will only change the AutoTune value. Be sure to include the desired values for these bits when changing the AutoTune value for these tag chips. For more information about Impinj M730/M750, Monza R6-A, Monza R6-B, and Monza R6-P, please refer to the datasheets available at

Reading and Changing the AutoTune Status

To read the AutoTune status using ItemTest, launch ItemTest and configure the reader to use "Dual Target" Search Mode. With a Mini-Guardrail antenna connected to the reader and a Monza R6 tag on the antenna, click "START" button. Assuming only the intended tag was inventoried, click "STOP" button, right click the result, and select "Tag Memory Access".

1.jpg Figure 2. Inventory tag

Next, read word 5 of Reserved memory. The result below was 3906h. Since 3h is 0011b, the AutoTune disable bit is 0, so AutoTune is enabled.


 Figure 3. AutoTune Enabled


Next, the value FFFFh is written to word 5.


 Figure 4. Command to Disable AutoTune


After the write command succeeds, read the word back to verify AutoTune has been disabled. Note that AutoTune cannot be changed if Monza R6 has been permalocked.


 Figure 5. AutoTune Disabled

The result now is B906h. Since bh is 1011h, this shows that bit A is high and AutoTune is now disabled.


To re-enable AutoTune, the value 0000h is written to word 5.


 Figure 6. Command to Enable AutoTune

Reading the value of word 5 one last time will confirm that AutoTune is again enabled.


 Figure 7. AutoTune Enabled


AutoTune has been successfully disabled/enabled!

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