VULCAN Technical Manual
Detailed hardware description
© 2007 Eurotech Ltd Issue D
21
Expansion bus
The expansion bus in the IXP425 network processor has 16 bit data and 24 bit
addresses for each of its eight independent chip selects. This allows an addressing
range of 512 bytes to 16MByte and connection of up to eight independent external
devices.
The chip selects of VULCAN devices connected to the expansion bus and
corresponding address spaces are listed in the following table. Chip select address
spaces relate to the expansion bus base address given in the main memory map.
Chip
select
Assignment
Size
Address space
(relative to base address)
Data bus
width
Access
CS0 Flash
16MB 0x00000000-
0x00FFFFFF
16b -
D[15:0]
R/W
CS1 Flash
(F32
variant)
16MB 0x01000000-
0x01FFFFFF
16b -
D[15:0]
R/W
CS2 SRAM
256KB 0x02000000-
0x0203FFFF
8b -
D[7:0]
R/W
UART (COM3) 8B
0x03000000-
0x03000007
CS3
UART (COM4) 8B
0x03000008-
0x0300000F
8b -
D[7:0]
R/W
CS4 GPIO
registers
1B
0x04000000-
0x040001FF
8b -
D[7:0]
R/W
CS5 WDT
set
register
1B 0x05000000-
0x050001FF
8b -
D[7:0]
R/W
CS6 Not
used
-
-
-
CS7 Not
used
-
-
-