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SAM9X25 [DATASHEET]
11054E–ATARM–10-Mar-2014
4.
An NOP command will be issued to the low-power DDR1-SDRAM. Program NOP command into the Mode Regis-
access to any DDR1-SDRAM address to acknowledge this command. Now clocks which drive DDR1-SDRAM
device are enabled.
A minimum pause of 200 s will be provided to precede any signal toggle.
5.
An all banks precharge command is issued to the low-power DDR1-SDRAM. Program all banks precharge com-
mand into the Mode Register, the application must set Mode to 2 in the Mode Register (See
Section 30.7.1 onpage 457). Perform a write access to any low-power DDR1-SDRAM address to acknowledge this command
6.
Two auto-refresh (CBR) cycles are provided. Program the auto refresh command (CBR) into the Mode Register,
to any low-power DDR1-SDRAM location twice to acknowledge these commands.
7.
An Extended Mode Register set (EMRS) cycle is issued to program the low-power DDR1-SDRAM parameters
and perform a write access to the SDRAM to acknowledge this command. The write address must be chosen so
that BA[1] is set to 1 BA[0] is set to 0. For example, with a 16-bit 128 MB SDRAM (12 rows, 9 columns, 4 banks)
bank address, the low-power DDR1-SDRAM write access should be done at address 0x20800000.
Note:
This address is for example purposes only. The real address is dependent on implementation in the product.
8.
A Mode Register set (MRS) cycle is issued to program the parameters of the low-power DDR1-SDRAM devices, in
particular CAS latency, burst length. The application must set Mode to 3 in the Mode Register (see
Section 30.7.1on page 457) and perform a write access to the low-power DDR1-SDRAM to acknowledge this command. The
write address must be chosen so that BA[1:0] bits are set to 0. For example, with a 16-bit 128 MB low-power
DDR1-SDRAM (12 rows, 9 columns, 4 banks) bank address, the SDRAM write access should be done at the
address 0x20000000. The application must go into Normal Mode, setting Mode to 0 in the Mode Register (see
acknowledge this command.
9.
Perform a write access to any low-power DDR1-SDRAM address.
10. Write the refresh rate into the count field in the DDRSDRC Refresh Timer register (see
page 458). (Refresh rate =
delay between refresh cycles). The low-power DDR1-SDRAM device requires a refresh every 15.625 s or 7.81
s. With a 100 MHz frequency, the refresh timer count register must to be set with (15.625*100 MHz) = 1562 i.e.
0x061A or (7.81*100 MHz) = 781 i.e. 0x030d
11. After initialization, the low-power DDR1-SDRAM device is fully functional.
30.4.3 DDR2-SDRAM Initialization
The initialization sequence is generated by software. The DDR2-SDRAM devices are initialized by the following
sequence:
1.
2.
Program the features of DDR2-SDRAM device into the Timing Register (asynchronous timing (trc, tras, etc.)), and
into the Configuration Register (number of columns, rows, banks, cas latency and output drive strength) (see
Sec-3.
An NOP command is issued to the DDR2-SDRAM. Program the NOP command into the Mode Register, the appli-
DDR2-SDRAM address to acknowledge this command. Now clocks which drive DDR2-SDRAM device are
enabled.
A minimum pause of 200 s is provided to precede any signal toggle.
4.
An NOP command is issued to the DDR2-SDRAM. Program the NOP command into the Mode Register, the appli-
DDR2-SDRAM address to acknowledge this command. Now CKE is driven high.
5.
An all banks precharge command is issued to the DDR2-SDRAM. Program all banks precharge command into the
form a write access to any DDR2-SDRAM address to acknowledge this command