UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
476 of 1269
NXP Semiconductors
UM10503
Chapter 21: LPC43xx External Memory Controller (EMC)
[1]
Clock enable must be HIGH during SDRAM initialization.
[2]
The memory controller exits from power-on reset with the self-refresh bit HIGH. To enter normal functional
mode set this bit LOW.
[3]
Disabling CLKOUT can be performed if there are no SDRAM memory transactions. When enabled this bit
can be used in conjunction with the dynamic memory clock control (CS) field.
21.7.5 Dynamic Memory Refresh Timer register
The DynamicRefresh register configures dynamic memory operation. It is recommended
that this register is modified during system initialization, or when there are no current or
outstanding transactions. This can be ensured by waiting until the EMC is idle, and then
entering low-power, or disabled mode. However, these control bits can, if necessary, be
altered during normal operation. This register is accessed with one wait state.
Note: This register is used for all four dynamic memory chip selects. Therefore the worst
case value for all of the chip selects must be programmed.
1
CS
Dynamic memory clock control. When clock control is LOW the
output clock CLKOUT is stopped when there are no SDRAM
transactions. The clock is also stopped during self-refresh mode.
1
0
CLKOUT stops when all SDRAMs are idle and during
self-refresh mode.
1
CLKOUT runs continuously (POR reset value).
2
SR
Self-refresh request, EMCSREFREQ. By writing 1 to this bit
self-refresh can be entered under software control. Writing 0 to
this bit returns the EMC to normal mode.
The self-refresh acknowledge bit in the Status register must be
polled to discover the current operating mode of the EMC.
1
0
Normal mode.
1
Enter self-refresh mode (POR reset value).
4:3
-
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
5
MMC
Memory clock control.
0
0
CLKOUT enabled (POR reset value).
1
CLKOUT disabled.
6
-
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
8:7
I
SDRAM initialization.
00
0x0
Issue SDRAM NORMAL operation command (POR reset value).
0x1
Issue SDRAM MODE command.
0x2
Issue SDRAM PALL (precharge all) command.
0x3
Issue SDRAM NOP (no operation) command)
13:9
-
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
31:14 -
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 357. Dynamic Control register (DYNAMICCONTROL - address 0x4000 5020) bit
description
Bit
Symbol
Value Description
Reset
value