Expansion Bus I/O Port Operation
8-17
Expansion Bus
8.4.2.2
Read FIFO Interface
The read FIFO interface can be accomplished gluelessly in XCE3 space or
with a small amount of glue in any XCE space. If a glueless read FIFO interface
is used (specified by boot configuration selection), the XOE signal is
only en-
abled in XCE3 space, and is dedicated to use for the FIFO interface. If this
mode is selected at boot, the
XOE signal is disabled in all other XCE spaces.
In this mode, XCE3 is used as the read enable signal and XOE is used as the
output enable signal of the FIFO. Figure 8–10 shows this interface
(Figure 8–11 shows the timing diagram for this interface). If the glueless read
FIFO mode is not chosen, then a minimal amount of glue can be used in any
XCE space specified as a FIFO interface. Figure 8–8 shows the required glue.
Figure 8–12 shows the timing diagram for the case when glue logic is used to
read from FIFO.
Figure 8–10. Glueless Read FIFO Interface
D[31:0]
WEN
WCLK
FIFO
Synchronous
Q[31:0]
HF
FF
EF
OE
REN
RCLK
bus
Expansion
XD[31:0]
EXT_INTx
XRE
XWE
XOE
XCE3
XFCLK
Figure 8–11.FIFO Read Mode – Read Timing (glueless case)
D5
D4
D3
D2
D1
XD[31:0]
XOE
XCE3
XFCLK
Sample5
Sample4
Sample3
Sample2
’C6000 sample1