X88C75 Datasheet, PDF (14/27 Pages) Xicor Inc. – Port Expander and E2 Memory

X88C75 SLIC^® E²
APPLICATION EXAMPLES
This section gives examples of most widely used em-
bedded systems architectures using the X88C75 and
80C51 microcontroller. However, keep in mind that
other microcontrollers are also supported by the X88C75
and/or other SLIC devices that Xicor manufactures.
Example 1
In this system, the X88C75 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 X88C75. This configura-
tion maps the EEM to a program/data memory address
in the range of 0000-1FFFH. The SFRM can be mapped
to any of the 64 x 1K pages within the data 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 X88C75 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 upper
program memory address space and out of the E²M
address range (0000-1FFFH.) This technique may also
be used for other external byte wide memories such as
SRAMs or EPROMs.
Figure 14. Example 1
8051
A15:8
AD7:0
ALE
WR
RD
PSEN
EA
X88C75
STRA
PA
STRB
ALE
PB
WR
RD
PSEN
CE RESET
2887 ILL F18
Figure 15. Example 2
8051
A15:8
AD7:0
ALE
WR
RD
PSEN
EA
X88C75
STRA
PA
STRB
ALE
PB ^A7:0
8
WR
RD
PSEN
CE RESET
A15
D7:0
A15:8
X28C256
A7-A0
CE
OE
WE
I/O7-I/O0
A14-A8
2887 ILL F19
14