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UM10503
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User manual
Rev. 2.1 — 10 December 2015
607 of 1441
NXP Semiconductors
UM10503
Chapter 23: LPC43xx/LPC43Sxx External Memory Controller (EMC)
23.7.9 Dynamic Memory Self Refresh Exit Time register
This 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.
23.7.10 Dynamic Memory Last Data Out to Active Time register
This 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.
23.7.11 Dynamic Memory Data In to Active Command Time register
This 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 423. 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 EMC_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 424. 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 EMC_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.
-