UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
94 of 362
NXP Semiconductors
UM10208
Chapter 8: LPC2800 EMC
10.4 Dynamic Memory Control Register (EMCDynamicControl -
0x8000 8020)
The EMCDynamicControl Register controls dynamic memory operation. The control bits
can be altered during normal operation.
Register.
Table 81.
Dynamic Control Register (EMCDynamicControl - address 0x8000 8020)
Bit
Symbol
Description
POR
Reset
Value
0
Force CKE
When this bit is 0, as it is after a power-on reset, the CKE output
to dynamic memory is driven high only during dynamic memory
operations, which saves power. Write a 1 to this bit at the start of
SDRAM initialization, to force CKE high continuously. Write a 0 to
this bit at the end of SDRAM initialization.
0
1
Force CLKOUT When this bit is 1, as it is after a power-on reset, CLKOUT to
dynamic memory runs continuously. Write a 0 to this bit to save
power by stopping CLKOUT when there are no SDRAM
transactions and during self-refresh mode.
1
2
Self-refresh
Request
When this bit is 1, as it after a power-on reset, dynamic memory
is placed in self-refresh mode. In self-refresh mode, data in
dynamic memory will be preserved if the LPC288x is stopped or
even powered down. Write 0 to this bit to switch the EMC and
dynamic memory to normal operating mode. Write a 1 to this bit
when the application is about to enter a low-power mode in which
it would not refresh dynamic memory. The self-refresh
acknowledge bit in the EMCStatus Register can be read to
determine the current operating mode of the EMC.
1
4:3
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
5
MMC
When this bit is 0, as it is after a power-on reset, the CLKOUT
signal is controlled by bit 1 as described above. Write a 1 to this
bit to completely stop/disable CLKOUT.
0
6
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
8:7
SDRAM
initialization
SDRAM initialization code needs to sequence this field to issue
commands to the dynamic memory, among the following values
in the order given:
11: NOP command
10: PALL command (precharge all)
01: MODE command
00: NORMAL command
See “SDRAM initialization” on page 110 for more information.
00
12:9
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-