GMS30C7201 Datasheet, PDF (77/352 Pages) Hynix Semiconductor – 60MHz operation frequency Low power consumption

SDRAM Controller
8.4 SDRAM Control Registers
The SDRAM controller has three registers: the configuration, refresh timer and the Write Buffer
Flush timer. The configuration register’s main function is to specify the number of SDRAMs
connected, and whether they are 2- or 4-bank devices. The refresh timer gives the number of
BCLK ticks that need to be counted in-between each refresh period. The Write Buffer Flush
timer is used to set the number of BCLK ticks since the last write operation, before the write
buffer’s contents are transferred to SDRAM.
Address
SDRAMCBase + 0x00
SDRAMCBase + 0x04
SDRAMCBase + 0x08
Name
Description
ConfigReg
#32-bit R/W
RefreshTmr
#16-bit R/W
Write buffer flush timer #3-bit R/W
Table 8-4: SDRAM controller registers
In addition to the SDRAM control registers, the ARM may access the SDRAM mode registers
by writing to a 64MByte address space referenced from the SDRAM mode register base
address. Writing to the SDRAM mode registers is discussed further in 8.5 Power-up
Initialization of the SDRAMs on page 8-10.
8.4.1 Configuration Register
Address: SDRAM register base address
31
S₁ S₀ - - -
--
23
15
R A C₁ C₀ D C W P E₃ B₃ - -
E₂ B₂ - -
7
E₁ B₁ - -
0
E₀ B₀ - -
The SDRAM controller configuration register is a 32-bit wide split read/write register, such that
bits [23:0] should be configured by the ARM, and bits [31:24] provide status information that
are read-only.
All locations containing “-” are for future expansion, and should always be programmed with
the binary value 0. Writes to bits [31:24] are always ignored.
E_[3:0]
Device Enable - indicates that there is a physical SDRAM present in each of
the four slots in the address map. This bit is used to determine whether an
auto-refresh command should be issued to a particular memory device.
slot 0 - address range 0–16Mbyte
slot 1 - address range 16–32MByte
slot 2 - address range 32–48MByte
slot 3 - address range 48–64MByte
Value = 1 if a device is present
Value = 0 if a device is not present
B_[3:0]
Indicates whether the SDRAM in the slot is a 2- or 4-bank device
Value = 1 if a four-bank device
GMS30C7201 Data Sheet
8-5