Slave FIFOs メモ書き⑤

page.233「15.5.3 PINFLAGSxx」について、


「Table 15-4. FIFO Flag Pin Functions」より、
「
FLAGA=PF, FLAGB=FF, FLAGC=EF, FLAGD=EP2PF
(Actual FIFO is selected by FIFOADR[0,1] pins)
」

ここで、page.103「9.2.4 FIFO Flag Pins (FLAGA, FLAGB, FLAGC, FLAGD)」より、
「
Four pins — FLAGA, FLAGB, FLAGC, and FLAGD (see
Figure 9-7) — report the status of the EZ-USB’s FIFOs; in
addition to the usual ‘FIFO full’ and ‘FIFO empty’ signals,
there is also a signal which indicates that a FIFO has filled to
a user-programmable level. The external master typically
monitors the ‘empty’ flag (EF) of OUT endpoints and the full
(FF) flag of IN endpoints; the programmable level flag (PF)
is equally useful for either type of endpoint (it can, for
instance, give advance warning that an OUT endpoint is
almost empty or that an IN endpoint is almost full).
」
empty flag (EF)
full flag      (FF)
programmable level flag (PF)