PSD813F2 datasheet(22/110 Pages) STMICROELECTRONICS

22 / 110 page

PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2

22/110

INSTRUCTIONS

An instruction consists of a sequence of specific

operations. Each received byte is sequentially de-

coded by the PSD and not executed as a standard

WRITE operation. The instruction is executed

when the correct number of bytes are properly re-

ceived and the time between two consecutive

bytes is shorter than the time-out period. Some in-

structions are structured to include READ opera-

tions after the initial WRITE operations.

The instruction must be followed exactly. Any in-

valid combination of instruction bytes or time-out

between two consecutive bytes while addressing

Flash memory resets the device logic into READ

Mode (Flash memory is read like a ROM device).

The PSD supports the instructions summarized in

Table 9., page 21:

Flash memory:

■

Erase memory by chip or sector

■

Suspend or resume sector erase

■

Program a Byte

■

Reset to READ Mode

■

Read primary Flash Identifier value

■

Read Sector Protection Status

■

Bypass (on the PSD833F2, PSD834F2,

PSD853F2 and PSD854F2)

These

instructions

are

detailed

Table

9., page 21. For efficient decoding of the instruc-

tions, the first two bytes of an instruction are the

coded cycles and are followed by an instruction

byte or confirmation byte. The coded cycles con-

sist of writing the data AAh to address X555h dur-

ing the first cycle and data 55h to address XAAAh

during the second cycle. Address signals A15-A12

are Don’t Care during the instruction WRITE cy-

cles. However, the appropriate Sector Select

(FS0-FS7 or CSBOOT0-CSBOOT3) must be se-

lected.

The primary and secondary Flash memories have

the same instruction set (except for Read Primary

Flash Identifier). The Sector Select signals deter-

mine which Flash memory is to receive and exe-

cute the instruction. The primary Flash memory is

selected if any one of Sector Select (FS0-FS7) is

High, and the secondary Flash memory is selected

any

one

Sector

Select

(CSBOOT0-

CSBOOT3) is High.

Power-up Mode

The PSD internal logic is reset upon Power-up to

the READ Mode. Sector Select (FS0-FS7 and

CSBOOT0-CSBOOT3) must be held Low, and

Write Strobe (WR, CNTL0) High, during Power-up

for maximum security of the data contents and to

remove the possibility of a byte being written on

the first edge of Write Strobe (WR, CNTL0). Any

WRITE cycle initiation is locked when VCC is be-

low VLKO.

READ

Under typical conditions, the MCU may read the

primary Flash memory or the secondary Flash

memory using READ operations just as it would a

ROM or RAM device. Alternately, the MCU may

use READ operations to obtain status information

about a Program or Erase cycle that is currently in

progress. Lastly, the MCU may use instructions to

read special data from these memory blocks. The

following sections describe these READ functions.

Read Memory Contents

Primary Flash memory and secondary Flash

memory are placed in the READ Mode after Pow-

er-up, chip reset, or a Reset Flash instruction (see

Table 9., page 21). The MCU can read the memo-

ry contents of the primary Flash memory or the

secondary Flash memory by using READ opera-

tions any time the READ operation is not part of an

instruction.

Read Primary Flash Identifier

The primary Flash memory identifier is read with

an instruction composed of 4 operations: 3 specific

WRITE operations and a READ operation (see Ta-

ble 9., page 21). During the READ operation, ad-

dress bits A6, A1, and A0 must be '0,0,1,'

respectively, and the appropriate Sector Select

(FS0-FS7) must be High. The identifier for the

PSD813F2/3/4/5 is E4h, and for the PSD83xF2 or

PSD85xF2 it is E7h.

Read Memory Sector Protection Status

The primary Flash memory Sector Protection Sta-

tus is read with an instruction composed of 4 oper-

ations: 3 specific WRITE operations and a READ

operation (see Table 9., page 21). During the

READ operation, address Bits A6, A1, and A0

must be '0,1,0,' respectively, while Sector Select

(FS0-FS7 or CSBOOT0-CSBOOT3) designates

the Flash memory sector whose protection has to

be verified. The READ operation produces 01h if

the Flash memory sector is protected, or 00h if the

sector is not protected.

The sector protection status for all NVM blocks

(primary Flash memory or secondary Flash mem-

ory) can also be read by the MCU accessing the

Flash Protection registers in PSD I/O space. See

the

section

entitled

Flash

Memory

Sector

Protect, page 28 for register definitions.

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