Expansion Bus I/O Port Operation
8-11
Expansion Bus
Figure 8–5 illustrates how to interface four 8-bit FIFOs to the I/O port (memory
map for this case is described in Table 8–7). Figure 8–6 is an example of inter-
face between two 16-bit FIFOs and the I/O port.
Figure 8–5. Example of the Expansion Bus Interface to Four 8-Bit FIFOs
Decoder
XD[31:24]
XD[23:16]
XD[15:8]
XD[7:0]
XA[3]
WEN
CLK
FIFO #3
D[7:0]
OE
REN
FIFO #2
WEN
REN
CLK
OE
D[7:0]
XA[2]
XRE
XCE
XD[31:0]
XOE
XFCLK
CLK
D[7:0]
OE
FIFO #4
REN
WEN
XD[31:0]
FIFO #1
REN
WEN
D[7:0]
OE
CLK
Table 8–6. Addressing Scheme – Case When Expansion Bus is Interfaced to
Four 8-Bit FIFOs
Logical Address
A[31:6]
A5
A4
A3
A2
A1
A0
FIFO #1 Address
X
X
X
0
0
0
0
FIFO #2 Address
X
X
X
0
1
0
1
FIFO #3 Address
X
X
X
1
0
1
0
FIFO #4 Address
X
X
X
1
1
1
1
Physical Address
XA5
XA4
XA3
XA2