UM10503
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User manual
Rev. 1.3 — 6 July 2012
480 of 1269
NXP Semiconductors
UM10503
Chapter 21: LPC43xx External Memory Controller (EMC)
21.7.12 Dynamic Memory Write Recovery Time register
The DYNAMICTWR register enables you to program the write recovery time, tWR. 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. This value is normally found in
SDRAM data sheets as tWR, tDPL, tRWL, or tRDL. 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.
21.7.13 Dynamic Memory Active to Active Command Period register
The DYNAMICTRC register enables you to program the active to active command period,
tRC. 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. This value is normally found
in SDRAM data sheets as tRC. 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.
Table 364. Dynamic Memory Data In to Active Command Time register (DYNAMICDAL -
address 0x4000 5040) bit description
Bit
Symbol Description
Reset
value
3:0
TDAL
Data-in to active command.
0x0 - 0xE = n clock cycles. The delay is in CCLK cycles.
0xF = 15 clock cycles (POR reset value).
0xF
31:4
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
-
Table 365. Dynamic Memory Write Recovery Time register (DYNAMICWR - address
0x4000 5044) bit description
Bit
Symbol Description
Reset
value
3:0
TWR
Write recovery time.
0x0 - 0xE = n + 1 clock cycles. The delay is in CCLK cycles.
0xF = 16 clock cycles (POR reset value).
0xF
31:4
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
-
Table 366. Dynamic Memory Active to Active Command Period register (DYNAMICRC -
address 0x4000 5048) bit description
Bit
Symbol
Description
Reset
value
4:0
TRC
Active to active command period.
0x0 - 0x1E = n + 1 clock cycles. The delay is in CCLK cycles.
0x1F = 32 clock cycles (POR reset value).
0x1F
31:5
-
Reserved, user software should not write ones to reserved bits. The
value read from a reserved bit is not defined.
-