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CHAPTER 4 BUS INTERFACE
4.3 Bus Interface
The bus interface include the following:
• Usual bus interface
• DRAM interface
These interfaces can only be used in the predetermined area.
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Chip Select Areas and Bus Interfaces
Table 4.3.1 shows the correspondence between each chip select area and available interface
functions.
The area mode register (AMD) specifies which interface to use. When not specified, the usual
bus interface is selected.
❍
DRAM interface
Two channels of DRAM interface are prepared and use areas 4 and 5.
• 3 types of DRAM interface
• Double CAS DRAM (usual DRAM interface)
• Single CAS DRAM
• Hyper DRAM
• High-speed page mode
• Selection of 2CAS/1WE and 1CAS/2WE
• CBR refresh system
• Selfrefresh mode
• Output of RAS and CAS programmable waveforms
Table 4.3-1 Correspondence between Chip Select Areas and Selectable Bus Interfaces
Area Selectable bus interface Remarks
Usual bus Time
sharing
DRAM
0 O - - Reset time
1O- -
2O- -
3O- -
4O-O
5O-O