AT91M40400-25C ATMEL Corporation, AT91M40400-25C Datasheet - Page 11

• Manufacturer Part Number: AT91M40400-25C
• Description: 16/32-bit Microcontroller, 2.7V to 3.6V Operating Range
• Manufacturer: ATMEL Corporation

Chip Select Lines
The EBI provides up to eight chip select lines:
•
•
By exchanging address lines for chip select lines, the user
can optimize the EBI to suit his external memory require-
ments: more external devices or larger address range for
each device.
Figure 6. Memory Connections for Four External Devices
Note:
Figure 7. Memory Connections for Eight External Devices
Note:
Chip select lines NCS0 - NCS3 are dedicated to the EBI
(not multiplexed).
Chip select lines CS4 - CS7 are multiplexed with the top
four address lines A23 - A20.
1.
1.
For four external devices, the maximum address space per device is 16M bytes.
For eight external devices, the maximum address space per device is 1M byte.
EBI
NCS0 - NCS3
CS4 - CS7
D0 - D15
A0 - A19
EBI
NWRx
NCS0 - NCS3
NRD
D0 - D15
A0 - A23
NWRx
NRD
8 or 16
The selection is controlled by the ALE field in EBI_MCR
(Memory Control Register). The following combinations are
possible:
NCS0
NCS1
A20, A21, A22, A23 (configuration by default)
A20, A21, A22, CS4
A20, A21, CS5, CS4
A20, CS6, CS5, CS4
CS7, CS6, CS5, CS4
8 or 16
NCS0
NCS2
D0 - D15 or D0 - D7
Memory Enable
Output Enable
Write Enable
A0 - A19
NCS1
NCS3
Memory Enable
NCS2
CS4
D0 - D15 or D0 - D7
NCS3
Memory Enable
Output Enable
Write Enable
A0 - A23
Memory Enable
CS5
Memory Enable
Memory Enable
CS6
Memory Enable
Memory Enable
CS7
Memory Enable
Memory Enable
Memory Enable
AT91M40400
Memory Enable
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