Tms320c32 8-, 16-, and 32-bit data memory – Texas Instruments TMS320C3x User Manual

Page 56

External Memory Interface

2-20

2.7.2

TMS320C32 8-, 16-, and 32-Bit Data Memory

The ’C32 external memory interface can load and store 8-, 16-, or 32-bit quanti-
ties into external memory and convert them into an internally-equivalent 32-bit
representation. The external memory interface accomplishes this without
changing the CPU instruction set. Figure 2–8 shows the supported external
memory widths, data types and sizes for zero wait-state memory and the asso-
ciated cycle count.

Figure 2–8. TMS320C32-Supported Data Types and Sizes and External Memory Widths

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Memory Width

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Data

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1-cycle read

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1-cycle read

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Type

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2-cycle read

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1-cycle read

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1-cycle read

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Size

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4-cycle read

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1-cycle read

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To access 8-, 16-, or 32-bit data quantities (types) from 8-, 16-, or 32-bit-wide
memory, the memory interface uses either strobe STRB0 or STRB1, depending
on the address location within the memory map. Each strobe consists of four pins
for byte enables and/or additional addresses. For a 32-bit memory interface, all
four pins are used as strobe byte-enable pins. These strobe byte-enable pins
select one or more bytes of the external memory. For a 16-bit memory interface,
the ’C32 uses one of these pins as an additional address pin, while using two
pins as strobe byte-enable pins. For an 8-bit memory interface, the ’C32 uses
two of these pins as additional address pins while using one pin as strobe pin.
The ’C32 manipulates the behavior of these pins according to the contents of
the bus control registers (one control register per strobe). By setting a few bit
fields in this register, you indicate the data-type size and external memory width.