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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
139 of 571
NXP Semiconductors
UM10316
Chapter 12: LPC29xx external Static Memory Controller (SMC)
3.
External memory interface
The external memory interface depends on the bank width: 32, 16 or 8 bits selected via
MW bits in the corresponding SMBCR register. Choice of memory chips requires an
adequate set-up of the RBLE bit in the same register. RBLE = 0 for 8-bit based external
memories, while memory chips capable of accepting 16- or 32-bit wide data will work with
RBLE = 1. If a memory bank is configured to be 32 bits wide, address lines A0 and A1 can
be used as non-address lines. Memory banks configured to 16 bits wide do not require
A0, while 8-bit wide memory banks require address lines down to A0.
Configuring A1 and/or A0 line(s) to provide address or non-address function is
accomplished by setting up the SCU. Symbol A[x] refers to the highest-order address line
of the memory chip used in the external-memory interface. CS refers to the eight bank-
select lines, and BLS refers to the four byte-lane select lines. WE_N is the write output
enable and OE_N is the output enable. Address pins on the device are shared with other
functions. When connecting external memories, check that the I/O pin is programmed to
the correct function. Control of these settings is handled by the SCU (see
).
shows configuration of a 32-bit wide memory bank using 8-bit devices.
and
show a 32-bit wide memory using 16- and 32-bit devices.
shows configuration of a 16-bit wide memory bank using 8-bit devices.
shows configuration of a 16-bit wide memory bank using 16-bit devices.
shows an 8-bit wide memory bank. This memory width requires 8-bit
devices.
32-bit bank using 8-bit devices
Fig 32. External memory interface: 32-bit banks with 8-bit devices
CS0 .. CS n
OE_N
CE
CE
CE
CE
OE
OE
OE
OE
WE
WE
WE
WE
IO[7:0]
IO[7:0]
IO[7:0]
IO[7:0]
A[x:0]
A[x:0]
A[x:0]
A[x:0]
D[31:24]
D[23:16]
D[15:8]
D[7:0]
BLS3
BLS0
BLS1
BLS2
A[x+2:2]