21
6174B–ATARM–07-Nov-05
AT91FR40162S Preliminary
Figure 10-1. External Memory Smaller than Page Size
10.2
External Bus Interface Pin Description
The following table shows how certain EBI signals are multiplexed:
1M Byte Device
1M Byte Device
1M Byte Device
1M Byte Device
Memory
Map
Hi
Low
Hi
Low
Hi
Low
Hi
Low
Base
Base + 1M Bytes
Base + 2M Bytes
Base + 3M Bytes
Base + 4M Bytes
Repeat 1
Repeat 2
Repeat 3
Table 10-1.
EBI Pin Description
Name
Description
Type
A0 - A23
Address bus (output)
Output
D0 - D15
Data bus (input/output)
I/O
NCS0 - NCS3
Active low chip selects (output)
Output
CS4 - CS7
Active high chip selects (output)
Output
NRD
Read enable (output)
Output
NWR0 - NWR1
Lower and upper write enable (output)
Output
NOE
Output enable (output)
Output
NWE
Write enable (output)
Output
NUB, NLB
Upper and lower byte select (output)
Output
NWAIT
Wait request (input)
Input
Table 10-2.
EBI Signals
Multiplexed Signals
Functions
A23 - A20
CS4 - CS7
Allows from 4 to 8 chip select lines to be used
A0
NLB
8- or 16-bit data bus
NRD
NOE
Byte write or byte select access
NWR0
NWE
Byte write or byte select access
NWR1
NUB
Byte write or byte select access