UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
99 of 362
NXP Semiconductors
UM10208
Chapter 8: LPC2800 EMC
10.12 Dynamic Memory Write Recovery Time Register (EMCDynamictWR -
0x8000 8044)
The EMCDynamicTWR Register controls the write recovery time, t
WR
. 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
WR
, t
DPL
, t
RWL
, or t
RDL
. This register is accessed with one wait state.
shows the bit assignments for the EMCDynamicTWR Register.
10.13 Dynamic Memory Active to Active Command Period Register
(EMCDynamictRC - 0x8000 8048)
The EMCDynamicTRC Register controls the active-to-active-command period, t
RC
. 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
RC
. This register is accessed with one wait state.
shows the EMCDynamictRC Register.
10.14 Dynamic Memory Auto-refresh Period Register (EMCDynamictRFC -
0x8000 804C)
The EMCDynamicTRFC Register controls the auto-refresh period, and
auto-refresh-to-active-command period, t
RFC
. This register should only be modified during
system initialization, or when there are no current or outstanding transactions. This can be
Table 89.
Dynamic Memory Write recover Time Register (EMCDynamictWR - address
0x8000 8044)
Bit
Symbol
Description
POR Reset
Value
3:0
Write
recovery time
(t
WR
)
SDRAM initialization code should write this field with one
less than the number of AHB HCLK cycles that equals or
just exceeds the tWR, tDPL, tRWL, or tRDL 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 90.
Dynamic Memory Active to Active Command Period Register (EMCDynamictRC -
address 0x8000 8048)
Bit
Symbol
Description
POR Reset
Value
4:0
Active-to-active-
command
period (t
RC
)
SDRAM initialization code should write this field with one
less than the number of AHB HCLK cycles that equals or
just exceeds the tRC time specified for the dynamic
memory. The power-on reset value would select 32 AHB
HCLK cycles.
0x1F
31:5
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
-