DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
148 of 571
NXP Semiconductors
UM10316
Chapter 12: LPC29xx external Static Memory Controller (SMC)
Sequential-access burst-reads from burst-flash devices of the same type as for burst
ROM are supported. Due to sharing of the SMBWST2R register between write and burst-
read transfers it is only possible to have one setting at a time for burst flash; either write
delay or the burst-read delay. This means that for write transfer the SMBWST2R register
must be programmed with the write-delay value, and for a burst-read transfer it must be
programmed with the burst-access delay.
The minimum wait-states value WST2 can be calculated from the following formula:
Where:
t
a(W)int
= internal write delay. For more information see
Dynamic characteristics.
t
emd(write)
= external-memory write delay in ns.
shows the bit assignment of the SMBWST2R0 to SMBWST2R7 registers.
4.4 Bank output enable assertion-delay control register
The bank output-enable assertion-delay 1 control register configures the delay between
the assertion of the chip-select and the output enable. This delay is used to reduce the
power consumption for memories that are unable to provide valid data immediately after
the chip-select is asserted. Since the access is timed by the wait-states, the programmed
value must be equal to or less than the bank wait-state 1 programmed value. The output
enable is always deasserted at the same time as the chip-select at the end of the transfer.
The bank configuration register contains the enable for output assertion delay.
shows the bit assignment of the SMBWSTOENR0 to SMBWSTOENR7
registers.
Table 108. SMBWST2Rn register bit description (SMBWRST1R0 to SMBWRST1R7,
addresses 0x6000 0008, 0x6000 0024, 0x6000 0040, 0x6000 005C, 0x6000 0078,
0x6000 0094, 0x6000 00B0, 0x6000 00CC)
* = reset value
Bit
Symbol
Access
Value
Description
31 to 5
reserved
R
-
Reserved; do not modify. Read as logic 0, write
as logic 0
4 to 0
WST2[4:0]
R/W
Wait-state 2. This register contains the length of
write accesses, except for burst ROM where it
defines the length of the burst-read accesses.
The write-access time c.q. the burst ROM read
access time is the programmed number of wait-
states multiplied by the system clock period
1Fh*
WST2
t
a W
( )
int
t
emd write
(
)
+
t
clk sys
(
)
------------------------------------------------
1
–
=