PSD4235G2-12UT datasheet(37/124 Pages) STMICROELECTRONICS

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PSD4235G2V

Instructions

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7.7

Data Polling (DQ7) - DQ15 for Motorola

When erasing or programming in Flash memory, the Data Polling bit (DQ7/DQ15) outputs

the complement of the bit being entered for programming/writing on the DQ7/DQ15 bit.

Once the Program instruction or the WRITE operation is completed, the true logic value is

read on the Data Polling bit (DQ7/DQ15, in a READ operation).

●

Data Polling is effective after the fourth WRITE pulse (for a Program instruction) or after

the sixth WRITE pulse (for an Erase instruction). It must be performed at the address

being programmed or at an address within the Flash memory sector being erased.

●

During an Erase cycle, the Data Polling bit (DQ7/DQ15) outputs a '0.' After completion

of the cycle, the Data Polling bit (DQ7/DQ15) outputs the last bit programmed (it is a ’1’

after erasing).

●

If the location to be programmed is in a protected Flash memory sector, the instruction

is ignored.

●

If all the Flash memory sectors to be erased are protected, the Data Polling bit

(DQ7/DQ15) is reset to ’0’ for about 100 µs, and then returns to the value from the

previously addressed location. No erasure is performed.

7.8

Toggle flag (DQ6) - DQ14 for Motorola

The PSD offers another way for determining when the Flash memory Program cycle is

completed. During the internal WRITE operation and when either FS0-FS7 or CSBOOT0-

CSBOOT3 is true, the Toggle Flag bit (DQ6/DQ14) bit toggles from 0 to ’1’ and 1 to ’0’ on

subsequent attempts to read any word of the memory.

When the internal cycle is complete, the toggling stops and the data read on the Data Bus

D0-D7 is the value from the addressed memory location. The device is now accessible for a

Table 29.

Status bits

DQ7

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

Data

Polling

Toggle

Flag

Error Flag

Erase

timeout

Table 30.

Status bits for Motorola(1)(2)(3)

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

DQ15-DQ0 represent the Data Bus bits, D15-D0.

FS0-FS7/CSBOOT0-CSBOOT3 are active high.

DQ15

DQ14

DQ13

DQ12

DQ11

DQ10

DQ9

DQ8

Data

Polling

Toggle

Flag

Error Flag

Erase

timeout

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