DSM2180F3 datasheet(13/63 Pages) STMICROELECTRONICS

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DSM2180F3

MEMORY MAP

Figure 7 shows a typical system memory map.

The nomenclature fs0..fs7 are individual 16K Byte

Flash memory segment designators. csiop desig-

nates the DSM control register block. The DSP

runs in Full Memory Mode. Memory contents of

the DSM device may lie in one or more of three dif-

ferent DSP address spaces; I/O space, Byte DMA

space, and/or External Data Overlay Memory

space. Since the DSM device is a byte-wide mem-

ory, it typically is not used in DSP Program Mem-

ory space (PMS active).

The designer may easily specify memory mapping

in a point-and-click software environment using

PSDsoft ExpressTM. Since the memory mapping is

implemented with the DPLD and the Page Regis-

ter, many possibilities exist. Figure 7 shows a typ-

ical memory map with the following attributes:

I/O Address Space. The 256 byte locations for

DSM control registers (csiop) reside in DSP I/O

address space, selected by the DSP IOMS signal.

Since DSP I/O accesses are by 16 bits, not 8 bits,

the upper byte of a 16-bit DSP I/O access must be

ignored.

Byte DMA Address Space. The DSP may boot-

load or fetch overlay bytes from 128K Bytes of

Flash memory using the DSP BDMA channel. The

DSP may also write to Flash memory using the

Byte DMA channel. DSM Flash memory is ac-

cessed in 128K continuous byte address locations

through the BDMA channel and is selected when-

ever the DSP BMS signal is active.

Flash memory in the DSM device must be un-

locked and written by the DSP one byte at a time,

checking status after each write (typical Flash

memory programming algorithm). A DMA channel

is not optimum for this scenario since the channel

must be initialized on each byte access. That is

why the 128K Bytes of Flash memory also lie in

DSP Data Overlay Memory space as described

next.

Data Overlay Memory Address Space. All

128K Bytes of Flash memory also reside in DSP

External Data Overlay Memory space, selected by

DMS

, allowing more efficient byte writes to Flash

memory. The DSP uses its external data overlay

window of 8K locations to access external memory

as data. The DSP doubles the size of this window

to 16K locations by manipulating its A13 address

line using its DMOVLAY register (See ADSP-218X

data sheets for details). Since all 128K Bytes of

Flash memory must be accessed through a win-

dow of only 16K locations, the DSP uses the Page

pages of 16K Bytes as shown in Figure 7. Since

DSP Data accesses are by 16 bits, not 8 bits, the

upper byte of a 16-bit DSP Data access must be

ignored.

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