Datasheet

2490R–AVR–02/2013

ATmega64(L)

• Bit 1 and Bit 6 MCUCR – SRW11, SRW10: Wait State Select Bits for Upper Sector

The SRW11 and SRW10 bits control the number of wait states for the upper sector of the exter-

nal memory address space, see Table 4.

• Bit 3..2 – SRW01, SRW00: Wait State Select Bits for Lower Sector

The SRW01 and SRW00 bits control the number of wait states for the lower sector of the exter-

nal memory address space, see Table 4.

Note: 1. n = 0 or 1 (lower/upper sector).

For further details of the timing and wait states of the External Memory Interface, see Figure

13 to Figure 16 how the setting of the SRW bits affects the timing.

• Bit 0 – Res: Reserved Bit

This is a reserved bit and will always read as zero. When writing to this address location, write

this bit to zero for compatibility with future devices.

Table 3. Sector Limits with Different Settings of SRL2..0

SRL2 SRL1 SRL0 Sector Limits

0 0 0 Lower sector = N/A

Upper sector = 0x1100 - 0xFFFF

0 0 1 Lower sector = 0x1100 - 0x1FFF

Upper sector = 0x2000 - 0xFFFF

0 1 0 Lower sector = 0x1100 - 0x3FFF

Upper sector = 0x4000 - 0xFFFF

0 1 1 Lower sector = 0x1100 - 0x5FFF

Upper sector = 0x6000 - 0xFFFF

1 0 0 Lower sector = 0x1100 - 0x7FFF

Upper sector = 0x8000 - 0xFFFF

1 0 1 Lower sector = 0x1100 - 0x9FFF

Upper sector = 0xA000 - 0xFFFF

1 1 0 Lower sector = 0x1100 - 0xBFFF

Upper sector = 0xC000 - 0xFFFF

1 1 1 Lower sector = 0x1100 - 0xDFFF

Upper sector = 0xE000 - 0xFFFF

Table 4. Wait States

(1)

SRWn1 SRWn0 Wait States

0 0 No wait states

0 1 Wait one cycle during read/write strobe

1 0 Wait two cycles during read/write strobe

Wait two cycles during read/write and wait one cycle before driving out

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