NEC uPD72257, Preliminary User'S Manual

Page: 311 / 343

9.4.2 Address adjustment
External addresses Depending on the selected bus width of the external memory the internal address,
which always describe byte addresses, may be shifted before they are output to
the external memory address bus. This way useless address bits are eliminated
and the addressable range of the external memory is increased, if memory with a
data bus larger than 8 bit is connected.
• external memory with 8-bit data bus
-
static memory setup: MEMSMCTRL.SDATAWn[2:0] = 100
B
- SDRAM setup: not supported
- external address output MA[24:0] = internal address
-
maximum memory 2
25
• 1 byte = 32 MB per chips select
• external memory with 16-bit data bus
-
static memory setup: MEMSMCTRL.SDATAWn[2:0] = 000
B
- SDRAM setup: MEMSCONR.DDATAW[1:0] = 00
B
- external address output MA[24:0] = internal address >> 1
-
maximum memory 2
25
• 2 byte = 64 MB per chips select
• external memory with 32-bit data bus
-
static memory setup: MEMSMCTRL.SDATAWn[2:0] = 001
B
- SDRAM setup: MEMSCONR.DDATAW[1:0] = 01
B
- external address output MA[24:0] = internal address >> 2
-
maximum memory 2
25
• 4 byte = 128 MB per chips select
External Memory Interface Controller Chapter 9
Preliminary User's Manual S19203EE1V3UM00
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