PSD813F2 datasheet(18/110 Pages) STMICROELECTRONICS

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PSD835G2

PSD8XX Family

9.1.1.2 Upper and Lower Block IN MAIN FLASH SECTOR

The PSD835G2’s main Flash has eight 64K bytes sector. The 64K byte sector size may

cause some difficulty in code mapping for an 8-bit MCU with only 64K byte address space.

To resolve this mapping issue, the PSD835G2 provides additional logic (Figure 3) for the

user to split the 8 sectors such that each sector has a lower and upper 32K byte block, and

the two blocks can reside in different pages but in the same address range.

If your design works with 64KB sectors, you don’t need to configure this logic. If the design

requires 32KB blocks in each sector, you need to define a “FA15” PLD equation in

PSDsoft as the A15 address input to the main Flash module. FA15 consists of 3 product

terms and will control whether the MCU is accessing the lower or upper 32KB in the

selected sector. Below is an example for Flash sector chip select FS0. A typical equation

is FA15 = pgr4 of the Page Register. When pgr4 is 0 (page 00), the lower 32KB is

selected. When pgr4 is switched to 1 by the user, the upper 32KB is selected. PSDsoft will

automatically generate the PLD equations shown, based on your point and click

selections.

page = [pgr7...pgr0]; “Page Register output

“Sector Chip Select Equation

FS0 = ((0000h <= address <= 7FFFh) & page = 00h) #

“select first 32KB block

((0000h <= address <= 7FFFh) & page = 10h);

“select second 32KB block

FA15 = pgr4;

“as address A15 input to the main Flash

If no FA15 equation is defined in PSDsoft, the A15 that comes from the MCU address bus

will be routed as input to the main Flash instead of FA15. The FA15 equation has no

impact in the Sector Erase operation. Note: FA15 affects all eight sectors of the main Flash

simultaneously, you cannot direct FA15 to a particular Flash sector only.

9.1.1.3 The Ready/Busy Pin (PE4)

Pin PE4 can be used to output the Ready/Busy status of the PSD835G2. The output on

the pin will be a ‘0’ (Busy) when Flash memory blocks are being written to, or when the

Flash memory block is being erased. The output will be a ‘1’ (Ready) when no write or

erase operation is in progress.

The

PSD835G2

Functional

Blocks

(cont.)

DPLD

ARRAY

FA15

A15

* Set by PSDsoft

FLASH CHIP SELECTS FS0-7

MUX

NVM CONTROL BIT

MAIN

FLASH

SECTOR

ADDR A15

A [14:0]

Figure 3. Selecting the Upper or Lower Block in a Main Flash Sector

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