![](http://datasheet.mmic.net.cn/280000/HMS30C7202N_datasheet_16073790/HMS30C7202N_49.png)
HMS30C7202N
2004 MagnaChip Semiconductor Ltd. All Rights Reserved. Version 1.1
- 44 -
7
STATIC MEMORY INTERFACE
The Static Memory Controller (SMI) interfaces the AMBA Advanced System Bus (ASB) to the External Bus
Interface (EBI). It controls four separate memory or expansion banks. Each bank is 32MB in size and can be
programmed individually to support:
z
8-, 16- or 32-bit wide, little-endian memory
z
Variable wait states (up to 16)
z
Burst mode read access
Burst mode access allows fast sequential access within quad word boundaries. This can significantly improve
bus bandwidth in reading from memory (that must support at least four word burst reads).
In addition, bus transfers can be extended using the EXPRDY input signal.
7.1
External Signals
Pin Name
Type
Description
EXPRDY
I
Expansion channel ready. When LOW, during phase one this signal will force the
current memory transfer to be extended.
nRWE [3:0]
O
These signals are active LOW write enables for each of the memory byte lanes
on the external bus.
nROE
O
This is the active LOW output enable for devices on the external bus.
nRCS [3:0]
O
Active LOW chip selects.
RA [24:0]
O
ROM Address Bus
RD [31:0]
I/O
ROM Data Bus
BOOTSBIT [1:0]
I
Configuration input.
00 - Select bank 0 as 32-bit memory
01 - Select bank 0 as 16-bit memory
10 - Select bank 0 as 8-bit memory
11 - Reserved
7.2
Functional Description
The main functions of the Static Memory Controller (SMI) are :
z
Memory bank select
z
Access sequencing
z
Wait states generation
z
Burst read control
z
Byte lane write control
These are described below
7.2.1
Memory bank select
Start Address
0 Mbytes
64 Mbytes
128 Mbytes
192 Mbytes
Address (Hex)
0x0000.0000
0x0400.0000
0x0800.0000
0x0C00.0000
Size
32Mbytes
32Mbytes
32Mbytes
32Mbytes
Description
ROM chip select 0
ROM chip select 1
ROM chip select 2
ROM chip select 3
7.2.2
Access sequencing
The bank configuration also determines the width of the external memory devices. When the external memory
bus is narrower than the transfer initiated from the current master, the internal transfer will take several
external bus transfers to complete. For example, in case that memory Bank0 is configured as 8-bit wide
memory and a 32-bit read is initiated the AMBA bus stalls while the SMI read four consecutive bytes from the