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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Memory Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
626
Order Number: 306262-004US
11.2.4
Overlapping Memory Regions
The MCU supports two independent memory regions:
• Memory Mapped Register (MMR) Space
• DDRI SDRAM Memory Space
The MMR memory space is fixed at CC00 E000H to CC00 FFFFH. Software programs the
DDRI SDRAM memory space by providing a base address in SDBR, each of the two
bank boundaries in SBR0 and SBR1.
For the IXP45X/IXP46X network processors, the two memory regions must never be
programmed to overlap.
11.2.5
DDRI SDRAM Clocking
The MCU provides 6 clocks to the DDRI SDRAM memory subsystem at the selected
DDRI SDRAM command rate. There are three positive clocks DDRI_CK[2:0] and three
negative clocks DDRI_CK_N[2:0]. The 72-bit 2-bank unbuffered JEDEC Standard
Double Data Rate (DDR) SDRAM Specification JESD79, June 2004 requires 6 clocks to
distribute the loading across eighteen x8 DDRI SDRAM components.
Note:
For IXP45X/IXP46X network processors, there will be a maximum of 10 chips (two
banks of x8 DRAM chips for a 40-bit bus).
11.2.6
Performance Monitoring
By setting up the system level PMU registers for the IXP45X/IXP46X network
processors, the following parameters can be monitored.
• Page hit and page miss counts for each of the 8 possible open pages of DDRI
SDRAM.
• AHB bus Read latency (from request to valid data back for each of the AHB bus
ports).
• Core memory bus read latency (from the Intel XScale processor to DDRI request to
valid data back for each of the eight outstanding read requests possible from the
Intel XScale processor to memory.
• The PMU status comes into the PMU event counters in the form of three different
buses. These are:
— DDRI_PMU_EVENT[4:0] where bit 4= valid, bit 3= hit/miss, bits 2:0 are the
page number
— BIU_PMU_RDACTIVE[7:0] where each bit is the enable for an active read in
progress
— DDRI_PMU_RDACTIVE[1:0] where bit 1 = South AHB read active and bit 0 =
North AHB read active