UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
108 of 362
NXP Semiconductors
UM10208
Chapter 8: LPC2800 EMC
10.26 Static Memory Turnaround Delay Registers (EMCStaticWaitTurn0-2 -
0x8000 8218,38,58)
The EMCStaticWaitTurn0-2 Registers control the number of bus turnaround cycles. These
registers should only be 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. These registers are accessed with one wait state.
shows the EMCStaticWaitTurn0-2 Registers.
To prevent bus contention on the external memory data bus, the WAITTURN field controls
the number of bus turnaround cycles added between static memory read and write
accesses. The WAITTURN field also controls the number of turnaround cycles between
static memory and dynamic memory accesses.
10.27 Static Memory Extended Wait Register (EMCStaticExtendedWait -
0x8000 8080)
This register controls the length of static memory read and write cycles if the
ExtendedWait (EW) bit in the EMCStaticConfig Register is 1. This register should only be
modified during system initialization, or when there are no current or outstanding
transactions. However, if necessary, these control bits can be altered during normal
operation. This register is accessed with one wait state.
shows the EMCStaticExtendedWait Register.
Table 103. Static Memory Write Delay Registers 0-2 (EMCStaticWaitWr0-2 - addresses
0x8000 8214, 0x8000 8234, 0x8000 8254)
Bit
Symbol
Description
Reset
Value
4:0
WAITWR
This field controls the length of write cycles. WE and BLS[1:0]
are asserted for (1) x t
HCLK
. Since the time from chip
select assertion to WE and BLS assertion is controlled by the
WAITWEN field in the EMCStaticWaitWen Register, and chip
select is asserted for one clock after WE and BLS are negated,
chip select is asserted for (W 3)
×
t
HCLK
.
The power-on reset value selects 32 AHB HCLK cycles for the
length of WE and BLS[1:0].
0x1F
31:5
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 104. Static Memory Turnaound Delay Registers 0-2 (EMCStaticWaitTurn0-2 - addresses
0x8000 8218, 0x8000 8238, 0x8000 8258)
Bit
Symbol
Description
Reset
Value
3:0
WAITTURN
Bus turnaround cycles in AHB HCLK cycles. Bus turnaround
time is (WA 1)
×
t
HCLK
.
0xF
31:4
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-