SLOA208B November 2014 – March 2019 TRF7970A , TRF7970A
After the anticollision procedures for Type A or Type B are completed, the data exchange layer is entered. Within the data exchange layer, the commands for Type 4A and Type 4B tag platforms are identical. Both Platforms also use the same frame formats.
The frame format for DEP packets at 106 kbps during data exchange (see Figure 7) is different than the frame format during anticollision. Depending on the command that is issued by the device only certain optional bytes are included.
The commands used by both tag platforms use the ISO 7816-4 specifications and are further defined in the NFC Forum T4TOP specifications. When an NFC enabled reader/writer is presented, the firmware allows for the selection of either supported tag type (Type 4A/B) during the anticollision process and then enters the data exchange layer.
Because the data exchange layer supports DEP commands for both tag platforms, the firmware allows has been designed to minimize size by using the same layer for both tag types. This is accomplished by only having a distinction between Type 4A and Type 4B tag platforms in the technology detection and anticollision sequences. This modularity gives the TRF7970A a more robust experience than basic static tags that are constrained to only working with one reader/writer type.