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1745D–ATARM–04-Nov-05
AT91M55800A
11. EBI: External Bus Interface
The EBI generates the signals that control the access to the external memory or peripheral
devices. The EBI is fully-programmable and can address up to 128M bytes. It has eight chip
selects and a 24-bit address bus.
The 16-bit data bus can be configured to interface with 8- or 16-bit external devices. Separate
read and write control signals allow for direct memory and peripheral interfacing.
The EBI supports different access protocols allowing single-clock cycle memory accesses.
The main features are:
• External memory mapping
• 8 active-low chip select lines
• 8- or 16-bit data bus
• Byte-write or byte-select lines
• Remap of boot memory
• Two different read protocols
• Programmable wait state generation
• External wait request
• Programmable data float time
The EBI User Interface is described on page 48.