UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
101 of 362
NXP Semiconductors
UM10208
Chapter 8: LPC2800 EMC
10.17 Dynamic Memory Load Mode Register to Active Command Time
(EMCDynamictMRD - 0x8000 8058)
The EMCDynamicTMRD Register controls the load mode register to active command
time, t
MRD
. This register should only be 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. This value is normally found
in SDRAM data sheets as t
MRD
or t
RSA
. This register is accessed with one wait state.
shows the EMCDynamicTMRD Register.
10.18 Dynamic Memory Configuration Register (EMCDynamicConfig -
0x8000 8100)
The EMCDynamicConfig Register enables you to program the configuration information
for the dynamic memory. These registers are normally only modified during system
initialization. These registers are accessed with one wait state.
shows the EMCDynamicConfig Register.
Table 93.
Dynamic Memory Active Bank A to Active Bank B Time Register
(EMCDynamictRRD - address 0x8000 8054)
Bit
Symbol
Description
POR Reset
Value
3:0
Active bank A to
active bank B
latency (t
RRD
)
SDRAM initialization code should write this field with one
less than the number of AHB HCLK cycles that equals or
just exceeds the tRRD time specified for the dynamic
memory. The power-on reset value would select 16 AHB
HCLK cycles.
0xF
31:4
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
-
Table 94.
Dynamic Memory Load Mode Register to Active Command Time
(EMCDynamictMRD - address 0x8000 8058)
Bit
Symbol
Description
POR Reset
Value
3:0
Load mode
register to active
command time
(t
MRD
)
SDRAM initialization code should write this field with one
less than the number of AHB HCLK cycles that equals or
just exceeds the tMRD or tRSA time specified for the
dynamic memory. The power-on reset value would select
16 AHB HCLK cycles.
0xF
31:4
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
-