
EZ-USB FX2 Technical Reference Manual
Page 9-4 EZ-USB FX2 Technical Reference Manual v2.1
9.2.2 FIFO Data Bus (FD)
The FIFO data bus, FD[x:0], can be either 8 or 16 bits wide. The width is selected via each FIFO’s
WORDWIDE bit, (EPxFIFOCFG.0):
• WORDWIDE=0: 8-bit mode. FD[7:0] replaces Port B. See Figure 9-4.
• WORDWIDE=1: 16-bit mode. FD[15:8] replaces Port D and FD[7:0] replaces Port B. See
Figure 9-5.
At power-on reset, the FIFO data bus defaults to 16-bit mode (WORDWIDE = 1) for all FIFOs.
In either mode, the FIFOADR[1:0] pins select which of the four FIFOs is internally connected to the
FD pins.
If
all
of the FIFOs are configured for 8-bit mode, Port D remains available for use as general-pur-
pose I/O. If
any
FIFO is configured for 16-bit mode, Port D is unavailable for use as general-pur-
pose I/O regardless of which FIFO is currently selected via the FIFOADR[1:0] pins.
Figure 9-4. 8-bit Mode Slave FIFOs, WORDWIDE=0
30/48MHz
FLAGA
FIFOADR[1:0]
Slave FIFOsFX2 Registers Device Pins
FLAGB
FLAGC
FLAGD/SLCS#
SLOE
SLRD
SLWR
PKTEND
FD[7:0]
EP4FIFOBUF
EP6FIFOBUF
EP8FIFOBUF
EP2FIFOBUF
EP8
EP6
EP4
EP2
IFCLK
5 - 48MHz
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