Rainbow Electronics W90N745CDG - Manual (Page 61)

W90N745CD/W90N745CDG
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6.3 External Bus Interface
6.3.1 EBI Overview
W90N745 supports External Bus Interface (EBI), which controls the access to the external memory
(ROM/FLASH, SDRAM) and External I/O devices. The EBI has seven chip selects to select one
ROM/FLASH bank, two SDRAM banks, and four External I/O banks.The address bus is 21 bits. It
supports 8-bit, 16-bit external data bus width for each bank.
The EBI has the following functions：
y SDRAM controller
y EBI control register
y ROM/FLASH interface
y External I/O interface
y External bus mastership
6.3.2 SDRAM Controller
The SDRAM controller module within W90N745 contains configuration registers 、 timing control
registers、common control register and other logic to provide 8、16 bits SDRAM interface with a single
8、16 bits SDRAM device or two 8-bit devices wired to give a 16-bit data path. The maximum size of
each bank is 64M bytes, and maximum memory size can span up to 128MB.
The SDRAM controller has the following features：
y Supports up to 2 external SDRAM banks
y Maximum size of each bank is 64M bytes
y 8、16-bit data interface
y Programmable CAS Latency： 1、2 and 3
y Fixed Burst Length： 1
y Sequential burst type
y Auto Refresh Mode and Self Refresh Mode
y Adjustable Refresh Rate
y Power up sequence