X68C75 Datasheet, PDF (14/26 Pages) Xicor Inc. – Port Expander and E2 Memory

X68C75 SLIC^® E²
APPLICATION EXAMPLES
This section gives examples of most widely used em-
bedded systems architectures using the X68C75 and
68HC11 microcontroller. However, keep in mind that
other microcontrollers are also supported by the X68C75
and/or other SLIC devices that Xicor manufactures.
Example 1
In this system, the X68C75 is the only parallel device
residing on the multiplexed address and data bus. There
may be other peripherals on the system board which are
controlled by the ports on the X68C75. This configura-
tion maps the EEM to a memory address in the range of
E000-FFFFH. The SFRM can be mapped to any of the
64 x 1K pages within the memory space.
Example 2
Applications requiring more than 8K bytes of program
memory space can be implemented using the basic
system architecture depicted in example 1 along with an
additional memory device such as the X28C256. Since
this device requires non-multiplexed address/data buses,
the X68C75 LAM feature is used to output the low order
address byte. The SFRM can be mapped to any 64x1K
page, but the X28C256 should be mapped to the low
memory address space and out of the E²M address
range (E000-FFFFH). This technique may also be used
for other external byte wide memories such as SRAMs
or EPROMs.
Figure 14. Example 1
68HC11
AS
R/W
E
X68C75
STRA
A[15:8]
AD[7:0]
PA
STRB
VCC
AS
R/W
E
SEL
CE
RESET
PB
VCC
2899 ILL F16
Figure 15. Example 2
68HC11
AS
R/W
E
X68C75
STRA
PA
A[15:8]
AD[7:0]
STRB
AS
PB ^A[7:0]
8
R/W
E
VCC
VCC
CE RESET
A15
D[7:0]
A[15:8]
X28C256
A7-A0
CE
OE
WE
I/O7-I/O0
A14-A8
2899 ILL F17
14