PSD913F2 datasheet(23/94 Pages) STMICROELECTRONICS

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Preliminary Information

PSD9XX Family

The

PSD9XX

Functional

Blocks

(cont.)

9.1.1.4 Power-Up Condition

The PSD9XX Flash memory is reset upon power-up to the read array mode. The FSi and

CSBOOTi select signals, along with the write strobe signal, must be in the false state

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 a write strobe signal. Any write cycle initiation is

locked when VCC is below VLKO.

9.1.1.5 Read

Under typical conditions, the microcontroller may read the Flash, or Secondary Flash

memories using read operations just as it would a ROM or RAM device. Alternately, the

microcontoller may use read operations to obtain status information about a program or

erase operation in progress. Lastly, the microcontroller may use instructions to read

special data from these memories. The following sections describe these read functions.

9.1.1.5.1 Read the Contents of Memory

Main Flash and Secondary Flash memories are placed in the read array mode after

power-up, chip reset, or a Reset Flash instruction (see Table 9). The microcontroller can

read the memory contents of main Flash or Secondary Flash by using read operations any

time the read operation is not part of an instruction sequence.

9.1.1.5.2 Read the Main Flash Memory Identifier

The main Flash memory identifier is read with an instruction composed of 4 operations:

3 specific write operations and a read operation (see Table 9). During the read operation,

address bits A6, A1, and A0 must be 0,0,1, respectively, and the appropriate sector select

signal (FSi) must be active. The PSD9XX main Flash memory ID is E7h (PSD934/954F2)

and E4h (PSD913F2).

9.1.1.5.3 Read the Flash Memory Sector Protection Status

The Flash memory sector protection status is read with an instruction composed of 4

operations: 3 specific write operations and a read operation (see Table 9). During the read

operation, address bits A6, A1, and A0 must be 0,1,0, respectively, while the chip select

(FSi or CSBOOTi) designates the Flash sector whose protection has to be verified. The

read operation will produce 01h if the Flash sector is protected, or 00h if the sector is not

protected.

The sector protection status for all NVM blocks (main Flash or Secondary Flash) can also

be read by the microcontroller accessing the Flash Protection and Secondary Flash

Protection registers in PSD I/O space. See section 9.1.1.9.1 for register definitions.

9.1.1.5.4 Read the Erase/Program Status Bits

The PSD9XX provides several status bits to be used by the microcontroller to confirm

the completion of an erase or programming instruction of Flash memory. These status bits

minimize the time that the microcontroller spends performing these tasks and are defined

in Table 10. The status bits can be read as many times as needed.

FSi/

CSBOOTi

DQ7

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

Data

Toggle

Error

Erase

Flash

VIH

Polling

Flag

Time-

out

Table 10. Status Bits

NOTES: 1. X = Not guaranteed value, can be read either 1 or 0.

2. DQ7-DQ0 represent the Data Bus bits, D7-D0.

3. FSi/CSBOOTi are active high.

For Flash memory, the microcontroller can perform a read operation to obtain these status

bits while an erase or program instruction is being executed by the embedded algorithm.

See section 9.1.1.7 for details.

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