ISSUE: Customers may find that tags with newer Monza4 chips void and older Monza4 tags do not with the same data stream.

Impinj released an updated version of the Monza4 chip with a change to the UMI bit function. More details from Impinj can be found here. This change can cause voids when attempting to print and encode on the RZx00, R110Xi4, ZD500R, ZE500R and ZT4x0R. The UMI (User Memory Indicator) bit is part of the PC (protocol control) bits, which is a portion of the EPC memory bank that tells a reader how much data is contained in the EPC. Because the UMI bit is now fixed, an attempt to rewrite it can cause the printer to void the tag. On the old chip, the PC bits were set to 3000 (96-bit EPC), and on the new chips, itís been changed to 3400.

There are several ways to determine if this change is causing the voids. One would be to look over the raw data going to the printer. If the following line is present, it may indicate the newer tags are causing the issue:


The opposite may be true if using the newer chips and the printer is sent the same data with ^FD3400.

If the customer is unsure which chip they have in use, they can send the following command to ask the printer to return to the host PC (Sending Printer Commands and Receiving Data) the PC bits programmed on the chip:



^FH_^HV11,,PC Bits:[,]_0D_0A,L^FS


This will return the value, which will be either 3000 or 3400, depending on if the newer or older chips are deployed.


The printers void because the verification of reading the chip after the attempted writing comes back with the old data, which in this case is the PC bits hardcoded into the chip. For the RZ400 and the R110Xi4, the recommendation is to either modify or remove the line entirely. Since the chip already has the PC bits encoded, it does not need to be programmed in again. The other resolution would be to modify the ZPL string to the printer to match the correct PC bits used by the chip to avoid the error.

For the Link-OS RFID printers, the ZT4x0R and the ZD500R, the above resolutions will work. There is, however, another resolution available. The ^RF command has a parameter to auto-adjust the PC bits when encoding the EPC data. Further details on utilizing the command are in the RFID Programming Guide in the Gen 2 memory bank section of the ^RF command.

If the customer is using mixed batches (old and new), removing the line entirely is the easiest course of action. If the customer must send the PC bits each time, they will have to update their ZPL each time they switch chips. This issue will clear up when the old chips stock the customer is using runs out and only uses the newer chips, thus eliminating the need to change with the chips.

Please note: some software utilities automatically include the PC bits in the data stream to the printer.