Datasheet

27
2490R–AVR–02/2013
ATmega64(L)
External Memory
Interface
With all the features that the External Memory Interface provides, it is well suited to operate as
an interface to memory devices such as external SRAM and Flash, and peripherals such as
LCD-display, A/D, and D/A. The main features are:
• Four different wait-state settings (Including no wait-state).
• Independent wait-state setting for different external memory sectors (configurable sector
size).
• The number of bits dedicated to address high byte is selectable.
• Bus Keepers on data lines to minimize current consumption (optional).
Overview When the eXternal MEMory (XMEM) is enabled, address space outside the internal SRAM
becomes available using the dedicated external memory pins (see Figure 1 on page 2, Table 27
on page 73, Table 33 on page 77, and Table 45 on page 85). The memory configuration is
shown in Figure 11.
Figure 11. External Memory with Sector Select
(1)
Note: 1. ATmega64 in non ATmega103 compatibility mode: Memory Configuration A is available (Mem-
ory Configuration B N/A).
ATmega64 in mega103 compatibility mode: Memory Configuration B is available (Memory
Configuration A N/A).
Memory Configuration A
0x0000
0x10FF
External Memory
(0-60K x 8)
0xFFFF
Internal Memory
SRL[2..0]
SRW11
SRW10
SRW01
SRW00
Lower Sector
Upper Sector
0x1100
Memory Configuration B
0x0000
External Memory
(0-60K x 8)
0xFFFF
Internal Memory
SRW10
0x0FFF
0x1000