UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
485 of 1269
NXP Semiconductors
UM10503
Chapter 21: LPC43xx External Memory Controller (EMC)
A chip select can be connected to a single memory device, in this case the chip select
data bus width is the same as the device width. Alternatively the chip select can be
connected to a number of external devices. In this case the chip select data bus width is
the sum of the memory device data bus widths.
For example, for a chip select connected to:
•
a 32-bit wide memory device, choose a 32-bit wide address mapping.
•
a 16-bit wide memory device, choose a 16-bit wide address mapping.
•
four x 8-bit wide memory devices, choose a 32-bit wide address mapping.
•
two x 8-bit wide memory devices, choose a 16-bit wide address mapping.
The SDRAM bank select pins BA1 and BA0 are connected to address lines A14 and A13,
respectively.
21.7.20 Dynamic Memory RAS & CAS Delay registers
The DynamicRasCas0:3 registers enable you to program the RAS and CAS latencies for
the relevant dynamic memory. It is recommended that these registers are 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.
Note: The values programmed into these registers must be consistent with the values
used to initialize the SDRAM memory device.
1
1
001
00
64 Mb (8Mx8), 4 banks, row length = 12, column length = 9
1
1
001
01
64 Mb (4Mx16), 4 banks, row length = 12, column length = 8
1
1
001
10
64 Mb (2Mx32), 4 banks, row length = 11, column length = 8
1
1
010
00
128 Mb (16Mx8), 4 banks, row length = 12, column length = 10
1
1
010
01
128 Mb (8Mx16), 4 banks, row length = 12, column length = 9
1
1
010
10
128 Mb (4Mx32), 4 banks, row length = 12, column length = 8
1
1
011
00
256 Mb (32Mx8), 4 banks, row length = 13, column length = 10
1
1
011
01
256 Mb (16Mx16), 4 banks, row length = 13, column length = 9
1
1
011
10
256 Mb (8Mx32), 4 banks, row length = 13, column length = 8
1
1
100
00
512 Mb (64Mx8), 4 banks, row length = 13, column length = 11
1
1
100
01
512 Mb (32Mx16), 4 banks, row length = 13, column length = 10
Table 373. Address mapping
14
12
11:9 8:7
Description