ST STM32F405 Reference Manual page 1679

RM0090
If a memory access is in progress, the Auto-refresh request is delayed. However, if the
memory access and Auto-refresh requests are generated simultaneously, the Auto-refresh
takes precedence. If the memory access occurs during a refresh operation, the request is
buffered to be processed when the refresh is complete.
This register common to SDRAM bank 1 and bank 2.
.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15
Bits 31: 15 Reserved, must be kept at reset value
Bit 14 REIE: RES Interrupt Enable
0: Interrupt is disabled
1: An Interrupt is generated if RE = 1
Bits 13:1 COUNT[12:0]: Refresh Timer Count
This 13-bit field defines the refresh rate of the SDRAM device. It is expressed in number of memory
clock cycles. It must be set at least to 41 SDRAM clock cycles (0x29).
COUNT = (SDRAM refresh rate x SDRAM clock frequency) - 20
SDRAM refresh rate = SDRAM refresh period / Number of rows
Bit 0 CRE: Clear Refresh error flag
This bit is used to clear the Refresh Error Flag (RE) in the Status Register.
0: no effect
1: Refresh Error flag is cleared
Note: The programmed COUNT value must not be equal to the sum of the following timings:
TWR+TRP+TRC+TRCD+4 memory clock cycles .
SDRAM Status register (FMC_SDSR)
Address offset: 0x158
Reset value: 0x0000 0000
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
Bits 31:5 Reserved, must be kept at reset value
Bit 5 BUSY: Busy status
This bit defines the status of the SDRAM controller after a Command Mode request
0: SDRAM Controller is ready to accept a new request
1; SDRAM Controller is not ready to accept a new request
Bits 4:3 MODES2[1:0]: Status Mode for Bank 2
This bit defines the Status Mode of SDRAM Bank 2.
00: Normal Mode
01: Self-refresh mode
10: Power-down mode
Reserved
Reserved
RM0090 Rev 18
Flexible memory controller (FMC)
14 13 12 11 10 9 8
REIE COUNT[12:0]
rw rw rw rw rw rw rw rw rw rw rw rw rw rw
9 8
7 6 5 4 3 2 1
CRE
7 6 5 4 3 2 1
r r r r r
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