UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
479 of 1269
NXP Semiconductors
UM10503
Chapter 21: LPC43xx External Memory Controller (EMC)
21.7.9 Dynamic Memory Self Refresh Exit Time register
The DYNAMICTSREX register enables you to program the self-refresh exit time, tSREX.
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 tSREX, for devices without this parameter you use the same
value as tXSR. 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.
21.7.10 Dynamic Memory Last Data Out to Active Time register
The DYNAMICTAPR register enables you to program the last-data-out to active command
time, tAPR. 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 tAPR. 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.
21.7.11 Dynamic Memory Data In to Active Command Time register
The DYNAMICTDAL register enables you to program the data-in to active command time,
tDAL. 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 tDAL, or tAPW. 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 362. Dynamic Memory Self Refresh Exit Time register (DYNAMICSREX - address
0x4000 5038) bit description
Bit
Symbol
Description
Reset
value
3:0
TSREX
Self-refresh exit 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 363. Dynamic Memory Last Data Out to Active Time register (DYNAMICAPR - address
0x4000 503C) bit description
Bit
Symbol
Description
Reset
value
3:0
TAPR
Last-data-out to active command 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.
-