NO:
W90P710 Programming Guide
VERSION:
2.1
PAGE:
28
The above information is the exclusive intellectual property of Winbond Electronics and shall not be disclosed,
distributed or reproduced without permission from Winbond.
Table No.: 1200-0003-07-A
SDRAM controller still refreshed SDRAM by every each specified refresh period. In this case, SDRAM
is closed not functioning by disabling CLKEN to save for power saving, and but SDRAM controller still
refreshes it to prevent from data lost. In sum, SDRAM is operated as follows :
NORMAL MODE :
REFEN=1
REFMOD=0
CLKEN=1
REFRAT=(proper
period)
POWER SAVING MODE 1 :
REFEN=1
REFMOD=0
CLKEN=1
REFRAT=(proper
period)
POWER SAVING MODE 2 :
REFEN=0
REFMOD=1
CLKEN=0
REFRAT=(don’t
care)
2.4.2 ROM/Flash control register
ROM/Flash control register is used to control the configuration of the boot ROM. In this register, the
size, base address, access type and access timing are specified. The base address of the boot ROM
can be set by BASADDR. Although the width of BASADDR is only 13 bits, the real start address of the
boot ROM is calculated as BASADDR << 18. Thus the range of the start address of the boot ROM is
from 0x0 to (2^13-1)*2^18. However, the system memory map should be concerned together when
setting the base address the base address setting should be checked to prevent from using
RESERVED memory address. The system memory map can be found in W90P710 spec data sheet.
After system reset, the EBI controller has uses the special power-on setting to ensure the boot
ROM to be bootable. These setting are as follows: