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External Memory Support
DSP56364 24-Bit Digital Signal Processor Users Manual, Rev. 2
3-8 Freescale Semiconductor
3.5 External Memory Support
The DSP56364 does not support the SSRAM memory type. It does support SRAM and DRAM as
indicated in the DSP56300 24-Bit Digital Signal Processor Family Manual, Freescale publication
DSP56300FM/AD. Note that the DSP56364 has only an 8-bit data bus. This means that no instruction
fetches from external memory are possible, and care should be taken to ensure that no program memory
instruction fetch access occurs in the external memory space. The DMA may be used to automatically pack
and unpack 24-bit data into the 8-bit wide external memory, during DMA data transfers.
Also, care should be taken when accessing external memory to ensure that the necessary address lines are
available. For example, when using glueless SRAM interfacing, it is possible to directly address 2
19
memory locations (512K) when using the 18 address lines and the two programmable address attribute
lines. Using DRAM access mode, the full 16M addressing range may be used.
3.6 Internal I/O Memory Map
The DSP56364 on-chip peripheral modules have their register files programmed to the addresses in the
internal X-I/O memory range (the top 128 locations of the X data memory space) as shown in Appendix
A, "Bootstrap ROM".