Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Expansion Bus
Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
654
Order Number: 306262-004US
The right side of
shows the implementation of bit 13:10 of the each Timing
and Control (EXP_TIMING_CS) Register. A Timing and Control (EXP_TIMING_CS)
Register is implemented for each of the eight chip selects. Each chip select defines a
base region size of 512 bytes with the actual size of the region given by the formula
shown in
. If the AHB address is outside of the programmed region, the
Expansion bus controller responds with an error response.
If there is a 32-MByte device programmed in any of the eight EXP_CS_TIMING
registers, a different memory map is used as shown in
. The lower 25 bits of
the AHB address are translated to the lower 25 bits of the Expansion Bus address,
EX_ADDR [24:0]. Bits 27:25 of the AHB are used to decode one of eight chip-select
regions implemented by the Expansion bus, each region being 32 Mbyte. If a design
Figure 124. Chip Select Address Allocation when there are no 32-MByte Devices
Programmed
B4398-01
cs_n[7]
128
MBytes
cs_n[0]
cs_n[1]
cs_n[2]
cs_n[3]
cs_n[4]
cs_n[5]
cs_n[6]
base + 0x1000000
base + 0x2000000
base + 0x3000000
base + 0x4000000
base + 0x5000000
base + 0x6000000
base + 0x7000000
base + 0x0000000
16 MB
0b0000 : 512 Bytes
CNFG[4:1] = 0b1111
SIZE = 16 MBytes
0b1110 : 8 MBytes
0b1101 : 4 MBytes
0b1100 : 2 MBytes
0b1011 : 1 MBytes
cs_n[x]
128
MBytes
cs_n[0] (alias)
.
..
base + 0x8000000
base + 0xFFFFFFF
Figure 125. Expansion Bus Memory Sizing
Region Size = 2
(9+CNFG[4:1] + 16*CNFG[0])
For Examples of how to use this feature:
If bits 13:9 of Timing and Control (EXP_TIMING_CS0) Register 0 = “00000” an
address space of 2
9
= 512 Bytes is defined for chip select 0 EX_CS_N[0].
If bits 13:9 of Timing and Control (EXP_TIMING_CS1) Register 1 = “10000” an
address space of 2
17
= 128KBytes is defined for chip select 1 EX_CS_N[1].
If bits 13:9 of Timing and Control (EXP_TIMING_CS2) Register 2 = “11110” an
address space of 2
24
= 16Mbytes is defined for chip select 2 EX_CS_N[2].
If bits 13:9 of Timing and Control (EXP_TIMING_CS7) Register 7 = “00001” an
address space of 2
25
= 32Mbytes is defined for chip select 7 EX_CS_N[7].