at91sam9g45 ATMEL Corporation, at91sam9g45 Datasheet - Page 22

• Manufacturer Part Number: at91sam9g45
• Description: At91 Arm Thumb-based Microcontrollers
• Manufacturer: ATMEL Corporation

7.1
7.2
7.2.1
22
Memory Mapping
Embedded Memories
AT91SAM9G45
Internal SRAM
A first level of address decoding is performed by the AHB Bus Matrix, i.e., the implementation of
the Advanced High performance Bus (AHB) for its Master and Slave interfaces with additional
features.
Decoding breaks up the 4 Gbytes of address space into 16 banks of 256 Mbytes. The banks 1 to
6 are directed to the EBI that associates these banks to the external chip selects NCS0 to
NCS5.
The bank 7 is directed to the DDRSDRC0 that associates this bank to DDR_NCS chip select
and so dedicated to the 4-port DDR2/ LPDDR controller.
The bank 0 is reserved for the addressing of the internal memories, and a second level of
decoding provides 1 Mbyte of internal memory area. The bank 15 is reserved for the peripherals
and provides access to the Advanced Peripheral Bus (APB).
Other areas are unused and performing an access within them provides an abort to the master
requesting such an access.
The AT91SAM9G45 product embeds a total of 64 Kbytes high-speed SRAM split in 4 blocks of
16 KBytes connected to one slave of the matrix. After reset and until the Remap Command is
performed, the four SRAM blocks are contiguous and only accessible at address 0x00300000.
After Remap, the SRAM also becomes available at address 0x0.
Figure 7-2.
The AT91SAM9G45 device embeds two memory features. The processor Tightly Coupled Mem-
ory Interface (TCM) that allows the processor to access the memory up to processor speed
(PCK) and the interface on the AHB side allowing masters to access the memory at AHB speed
(MCK).
A wait state is necessary to access the TCM at 400 MHz. Setting the bit NWS_TCM in the bus
Matrix TCM Configuration Register of the matrix inserts a wait state on the ITCM and DTCM
accesses.
0x00300000
Internal SRAM Reset
RAM
64K
Remap
RAM
64K
6438CS–ATARM–13-Oct-09
0x00000000