This example shows how external devices such as external SRAM and FLASH, and

peripherals such as LCD-display, A/D, and D/A can be access with the

External Memory Interface.



To enable the External Memory Interface, the SRE bit must be set in the

MCUCR register and optionally one or more wait states.



When the AT90S8515 is operated in the external SRAM mode, port A is used as

a multiplexed low-order address bus and data bus while port C is is used as

high order address bus.



In this example data is written to external memory location $4000 and read

back and output to LED connected to port B.



Note:

When using AVR Studio 4 for simulation, External Memory Interface must be

enabled using the menu Option

"Debug -> AVR Simulator Options -> Device Selection and select check box

"External Memory Interface"