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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
149 of 571
NXP Semiconductors
UM10316
Chapter 12: LPC29xx external Static Memory Controller (SMC)
4.5 Bank write-enable assertion-delay control register
The bank write-enable assertion-delay 1 control register configures the delay between the
assertion of the chip-select and the write enable. This delay is used to reduce power
consumption for memories. Since the access is timed by the wait-states the programmed
value must be equal to or less than the bank wait-state 2 programmed value. The write
enable is asserted half a system-clock cycle after assertion of the chip-select for logic 0
wait-states. The write enable is deasserted half a system-clock cycle before the
chip-select, at the end of the transfer. The byte-lane select outputs have the same timing
as the write-enable output for writes to 8-bit devices that use the byte-lane selects instead
of the write enables. The bank configuration register contains the enable for output
assertion delay.
shows the bit assignment of the SMBWSTWENR0 to SMBWSTWENR7
registers.
4.6 Bank configuration register
The bank configuration register defines bank access for the connected memory device.
A data transfer can be initiated to the external memory greater than the width of the
external-memory data bus. In this case the external transfer is automatically split up into
several separate transfers.
Table 109. SMBWSTOENRn register bit description (SMBWSTOENR0 to SMBWSTOENR7,
addresses 0x6000 000C, 0x6000 0028, 0x6000 0044, 0x6000 0060, 0x6000 007C,
0x6000 0098, 0x6000 00B4, 0x6000 00D0)
* = reset value
Bit
Symbol
Access
Value
Description
31 to 4
reserved
R
-
Reserved; do not modify. Read as logic 0, write
as logic 0.
3 to 0
WSTOEN
R/W
Output-enable assertion delay. This register
contains the length of the output-enable delay
after the chip-select assertion. The output-
enable assertion-delay time is the programmed
number of wait-states multiplied by the system
clock period
0h*
Table 110. SMBWSTWENRn register bit description (SMBWSTWENR0 toSMBWSTWENR7,
addresses 0x6000 0010, 0x6000 002C, 0x6000 0048, 0x6000 0064, 0x6000 0080,
0x6000 009C, 0x6000 00B8, 0x6000 00D4)
* = reset value
Bit
Symbol
Access
Value
Description
31 to 4
reserved
R
-
Reserved; do not modify. Read as logic 0, write
as logic 0
3 to 0
WSTWEN
R/W
Write-enable assertion delay. This register
contains the length of the write enable delay
after the chip-select assertion. The write-enable
assertion-delay time is the programmed
number of wait-states multiplied by the system
clock period
1h*