UPSD3422 datasheet(19/293 Pages) STMICROELECTRONICS

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uPSD34xx

Memory organization

19/293

Memory organization

The 8032 MCU core views memory on the MCU module as “internal” memory and it views

memory on the PSD module as “external” memory, see Figure 6

Internal memory on the MCU Module consists of DATA, IDATA, and SFRs. These standard

8032 memories reside in 384 bytes of SRAM located at a fixed address space starting at

address 0x0000.

External memory on the PSD Module consists of four types: main Flash (64K, 128K, or

256K bytes), a smaller secondary Flash (32K), SRAM (4K, 8K or 32Kbytes), and a block of

PSD Module control registers called csiop (256 bytes). These external memories reside at

programmable address ranges, specified using the software tool PSDsoft Express. See the

PSD Module section of this document for more details on these memories.

External memory is accessed by the 8032 in two separate 64K byte address spaces. One

address space is for program memory and the other address space is for data memory.

Program memory is accessed using the 8032 signal, PSEN. Data memory is accessed

using the 8032 signals, RD and WR. If the 8032 needs to access more than 64K bytes of

external program or data memory, it must use paging (or banking) techniques provided by

the Page Register in the PSD Module.

Note:

When referencing program and data memory spaces, it has nothing to do with 8032 internal

SRAM areas of DATA, IDATA, and SFR on the MCU Module. Program and data memory

spaces only relate to the external memories on the PSD Module.

External memory on the PSD Module can overlap the internal SRAM memory on the MCU

Module in the same physical address range (starting at 0x0000) without interference

because the 8032 core does not assert the RD or WR signals when accessing internal

SRAM.

Figure 6.

uPSD34xx memories

• External memories may be placed at virtually

any address using software tool PSDsoft Express.

• The SRAM and Flash memories may be placed

in 8032 Program Space or Data Space using

PSDsoft Express.

• Any memory in 8032 Data Space is XDATA.

64KB

128KB

256KB

32KB

Main

Flash

Internal SRAM on

MCU Module

External Memory on

PSD Module

IDATA

SFR

DATA

Secondary

Flash

4KB

8KB

32KB

SRAM

384 Bytes SRAM

Direct or Indirect Addressing

128 Bytes

Indirect

Addressing

Fixed

Addresses

Direct

Addressing

AI10410b

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