PSD4235G2-12UT datasheet(41/124 Pages) STMICROELECTRONICS

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PSD4235G2V

Programming Flash memory

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since the Toggle Flag bit (DQ6/DQ14) may have changed simultaneously with the Error Flag

bit (DQ5/DQ13, see Figure 6).

The Error Flag bit (DQ5/DQ13) is set if either an internal timeout occurred while the

embedded algorithm attempted to program, or if the MCU attempted to program a ’1’ to a bit

that was not erased (not erased is logic 0).

It is suggested (as with all Flash memories) to read the location again after the embedded

programming algorithm has completed, to compare the word that was written to Flash

memory with the word that was intended to be written.

When using the Data Toggle method after an Erase cycle, Figure 6 still applies. the Toggle

Flag bit (DQ6/DQ14) toggles until the Erase cycle is complete. A '1' on the Error Flag bit

(DQ5/DQ13) indicates a timeout condition on the Erase cycle, a ’0’ indicates no error. The

MCU can read any even location within the sector being erased to get the Toggle Flag bit

(DQ6/DQ14) and the Error Flag bit (DQ5/DQ13).

PSDsoft Express generates ANSI C code functions which implement these Data Toggling

algorithms.

8.3

Unlock Bypass

The Unlock Bypass instruction allows the system to program words to the Flash memories

faster than using the standard Program instruction. The Unlock Bypass mode is entered by

first initiating two Unlock cycles. This is followed by a third WRITE cycle containing the

Unlock Bypass command, 20h (as shown in Table 28). The Flash memory then enters the

Unlock Bypass mode.

A two-cycle Unlock Bypass Program instruction is all that is required to program in this

mode. The first cycle in this instruction contains the Unlock Bypass Program command,

A0h. The second cycle contains the program address and data. Additional data is

programmed in the same manner. This mode dispense with the initial two Unlock cycles

required in the standard Program instruction, resulting in faster total programming time.

During the unlock bypass mode, only the Unlock Bypass Program and Unlock Bypass Reset

instructions are valid.

To exit the Unlock Bypass mode, the system must issue the two-cycle Unlock Bypass Reset

instruction. The first cycle must contain the data 90h; the second cycle the data 00h.

Addresses are Don’t Care for both cycles. The Flash memory then returns to READ mode.

PSD4235G2-12UT Datasheet(PDF) 41 Page - STMicroelectronics