UPSD3422 datasheet(196/293 Pages) STMICROELECTRONICS

196 / 293 page

PSD module

uPSD34xx

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from the Secondary Flash memory in program space. After the writing is complete, the Main

Flash can be “reclassified” back to program space, then execution can continue from the

new code in Main Flash memory. The mapping example of Figure 68 will accommodate this

operation.

28.2.6

Memory sector select rules

When defining sector select signals (FSx, CSBOOTx, RS0, CSIOP, PSELx) in PSDsoft

Express, the user must keep these rules in mind:

●

Main Flash and Secondary Flash memory sector select signals may not be larger than

their physical sector size as defined in Table 101 on page 187.

●

Any Main Flash memory sector select may not be mapped in the same address range

as another Main Flash sector select (cannot overlap segments of Main Flash on top of

each other).

●

Any Secondary Flash memory sector select may not be mapped in the same address

range as another Secondary Flash sector select (cannot overlap segments of

Secondary Flash on top of each other).

●

A Secondary Flash memory sector may overlap a Main Flash memory sector. In the

case of overlap, priority is given to the Secondary Flash memory sector.

●

SRAM, CSIOP, or PSELx may overlap any Flash memory sector. In the case of overlap,

priority is given to SRAM, CSIOP, or PSELx.

Note:

PSELx is for optional Peripheral I/O Mode on Port A.

●

The address range for sector selects for SRAM, PSELx, and CSIOP must not overlap

each other as they have the same priority, causing contention if overlapped.

Figure 69 illustrates the priority scheme of the memory elements of the PSD Module.

Priority refers to which memory will ultimately produce a byte of data or code to the 8032

MCU for a given bus cycle. Any memory on a higher level can overlap and has priority over

any memory on a lower level. Memories on the same level must not overlap.

Example: FS0 is valid when the 8032 produces an address in the range of 8000h to BFFFh.

CSBOOT0 is valid from 8000h to 9FFFh. RS0 is valid from 8000h to 87FFh. Any address

from the 8032 in the range of RS0 always accesses the SRAM. Any address in the range of

CSBOOT0 greater than 87FFh (and less than 9FFFh) automatically addresses Secondary

Flash memory. Any address greater than 9FFFh accesses Main Flash memory. One-half of

the Main Flash memory segment and one-fourth of the Secondary Flash memory segment

cannot be accessed by the 8032.

Figure 69.

PSD module memory priority

Level 1

SRAM,

CSIOP, and

Peripheral I/O

Mode

Highest Priority

Level 2

Secondary

Flash Memory

Level 3

Main Flash Memory

Lowest Priority

AI02867E

UPSD3422 Datasheet(PDF) 196 Page - STMicroelectronics

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