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AT32F435/437
Series Reference Manual
2022.11.11
Page 532
Rev 2.03
24.6.2 Self-refresh mode and Power-down mode
The SDRAM controller supports two low-power modes: self-refresh mode and power-down mode.
Self-refresh mode
This mode is selected by setting CMD=101 and by configuring the Target Bank bits (BK1 and/or BK2) in
the SDRAM_CMD register.
The SDRAM clock stops running after a TRAS delay. The internal refresh time stops counting if one of
the following conditions is present:
When both SDRAM devices have been initialized, a self-refresh command is issued to both devices; or
when one of the devices is not initialized, a self-refresh command is issued to one of the device.
After entering the self-refresh mode, the SDRAM device must remain in this mode for a minimum period
of time of TRAS, which is determined by the SDRAM device characteristics. To guarantee this minimum
period, the BUSY flag will be set after the self-refresh is entered. The BUSY flag is cleared automatically
only after a TRAS time. This bit can be used to judge whether to exit self-refresh mode.
It is possible to leave self-refresh mode by setting CMD=000 or by read/write access to the SDRAM.
Power-down mode
This mode is selected by setting CMD=110 and by configuring the Target Bank bits (BK1 and/or BK2) in
the SDRAM_CMD register.
During power-down mode, the SDRAM device can also perform auto-refresh operation. When an auto-
refresh command occurs, the SDRAM exists from the power-down mode before performing auto-refresh
operation. After that, the SDRAM will enter power-down mode again.
It is possible to leave power-down mode by setting CMD=000 or by read/write access to the SDRAM.
24.7 XMC registers
These peripheral registers must be accessed by word (32 bits).
Table 24-39
XMC register address mapping
Register name
Offset
Reset value
XMC_BK1CTRL1
0x000
0x0000 30DB
XMC_BK1TMG1
0x004
0x0FFF FFFF
XMC_BK1CTRL2
0x008
0x0000 30D2
XMC_BK1TMG2
0x00C
0x0FFF FFFF
XMC_BK1CTRL3
0x010
0x0000 30D2
XMC_BK1TMG3
0x014
0x0FFF FFFF
XMC_BK1CTRL4
0x018
0x0000 30D2
XMC_BK1TMG4
0x01C
0x0FFF FFFF
XMC_BK2CTRL
0x060
0x0000 0018
XMC_BK2IS
0x064
0x0000 0040
XMC_BK2TMGRG
0x068
0xFCFC FCFC
XMC_BK2TMGSP
0x06C
0xFCFC FCFC
XMC_BK2ECC
0x074
0x0000 0000
XMC_BK3CTRL
0x080
0x0000 0018
XMC_BK3IS
0x084
0x0000 0040
XMC_BK3TMGRG
0x088
0xFCFC FCFC
XMC_BK3TMGSP
0x08C
0xFCFC FCFC
XMC_BK3ECC
0x094
0x0000 0000
XMC_BK4CTRL
0x0A0
0x0000 0018
XMC_BK4IS
0x0A4
0x0000 0040