Texas Instruments TMS320C6727 External Memory Interface Emif, Emif Device-Specific Information

TMS320C6727, TMS320C6726, TMS320C6722

Floating-Point Digital Signal Processors

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SPRS268E –MAY 2005 –REVISED JANUARY 2007

4.11 External Memory Interface (EMIF)

4.11.1 EMIF Device-Specific Information

The C672x DSP includes an external memory interface (EMIF) for optional SDRAM, NOR FLASH, NAND FLASH, or SRAM. The key features of this EMIF are:

∙One chip select (EM_CS[0]) dedicated for x16 and x32 SDRAM (x8 not supported)

∙One chip select (EM_CS[2]) dedicated for x8, x16, or x32 NOR FLASH; x8, x16, or x32 Asynchronous SRAM; or x8 or x16 NAND FLASH

∙Data bus width is 16 bits on the C6726 and C6722, and 32 bits on the C6727

∙SDRAM burst length of 16 bytes

∙External Wait Input on the C6727 through EM_WAIT (programmable active-high or active-low)

∙External Wait pin functions as an interrupt for NAND Flash support

∙NAND Flash logic calculates ECC on blocks of up to 512 bytes

∙ECC logic suitable for single-bit errors

Figure 4-5and Figure 4-6show typical examples of EMIF-to-memory hookup on the C672x DSP.

As the figures illustrate, the C672x DSP includes a limited number of EMIF address lines. These are sufficient to connect to SDRAM seamlessly. Asynchronous memory such as FLASH typically will need to use additional GPIO pins to act as upper address lines during device boot up when the FLASH contents are copied into SDRAM. (Normally, code is executed from SDRAM since SDRAM has faster access times).

Any pins listed with a ‘Y'in the GPIO column of Table 2-12may be used for this purpose, as long as it can be assured that they be pulled low at (and after) reset and held low until configured as outputs by the DSP.

Note that EM_BA[1:0] are used as low-order address lines for the asynchronous interface. For example, in Figure 4-5and Figure 4-6, the flash memory is not byte-addressable and its A[0] input selects a 16-bit value. The corresponding DSP address comes from EM_BA[1]. The remaining address lines from the DSP (EM_A[12:0]) drive a word address into the flash inputs A[13:1].

For a more detailed explanation of the C672x EMIF operation please refer to the document TMS320C672x External Memory Interface (EMIF) User's Guide (literature number SPRU711).

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