TMP91C824
91C824-89
2008-02-20
3.6.3
Connecting External Memory
Figure 3.6.6 shows an example of how to connect external memory to the TMP91C824.
In this example the ROM is connected using a 16-bit bus. The RAM and I/O are
connected using an 8-bit bus.
Figure 3.6.6 Example of External Memory Connection
(ROM uses 16-bit bus; RAM and I/O use 8-bit bus.)
A reset clears all bits of the port 6 control register P6CR and the port 6 function
register P6FC to 0 and disables output of the CS signal. To output the CS signal, the
appropriate bit must be set to 1.
Figure 3.6.7 Example of External Memory Connection (RAM and I/O use 16-bit bus)
74AC08
Not connect
Address bus
CS
8-bit
RAM
OE WE
TMP91C824
CS
Upper byte
ROM
OE
CS
Lower byte
ROM
OE
CS
8-bit
I/O
OE WE
0
CS
1
CS
2
CS
A0
A23
D8
D15
D0
D7
RD
WR
to
to
to
OE
LDS
UDS
R/W
CE
I/O [16:1]
A0
A1
A2
RD
WR
HWR
R/W
CS0
D [15:0]
A0
A1
A2
A3
TMP91C824FG 16-bit
SRAM