Panasonic FP7 Series Command Reference Manual page 427

8.18 FIFR (Data Read (First-In-First-Out))
Name Description
To be set when "[S]+1" (stored data amount) is larger than [S] (buffer size).
To be set when "[S] +2" (read pointer) is greater than or equal to [S] (buffer size).
To be set when the buffer area exceeds the upper limit of a specified device.
WUME-FP7CPUPGR-12 8-39