PSD4235G2 datasheet(30/93 Pages) STMICROELECTRONICS

30 / 93 page

Preliminary Information

PSD4000 Series

The

PSD4000

Functional

Blocks

(cont.)

Level 1

SRAM, I /O

Level 2

Secondary Flash Memory

Highest Priority

Lowest Priority

Level 3

Main Flash Memory

Figure 5. Priority Level of Memory and I/O Components

9.1.3.1. Memory Select Configuration for MCUs with Separate Program and Data Spaces

The 80C51XA and compatible family of microcontrollers, can be configured to have

separate address spaces for code memory (selected using PSEN) and data memory

(selected using RD). Any of the memories within the PSD4000 can reside in either space

or both spaces. This is controlled through manipulation of the VM register that resides in

the PSD’s CSIOP space.

The VM register is set using PSDsoft to have an initial value. It can subsequently be

changed by the microcontroller so that memory mapping can be changed on-the-fly.

For example, you may wish to have SRAM and main Flash in Data Space at boot, and

secondary Flash memory in Program Space at boot, and later swap main and secondary

Flash memory. This is easily done with the VM register by using PSDsoft to configure it for

boot up and having the microcontroller change it when desired.

Table 11 describes the VM Register.

Bit 7

Bit 6* Bit 5*

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

PIO_EN

FL_Data Boot_Data

FL_Code

Boot_Code SRAM_Code

0 = disable

0 = RD

0 = PSEN

PIO mode

can’t

access

Flash

Boot Flash

Flash

Boot Flash

SRAM

1= enable

1 = RD

1 = PSEN

PIO mode

access

Flash

Boot Flash

Flash

Boot Flash

SRAM

Table 11. VM Register

NOTE: Bits 6-5 are not used.

PSD4235G2 Scheda tecnica(PDF) 30 Page - STMicroelectronics

PSD4235G2 Scheda tecnica(HTML) 30 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93

Scheda tecnica Scarica

Link URL