PSD935G2 datasheet(23/91 Pages) STMICROELECTRONICS

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PSD9XX Family

PSD935G2

Figure 4. Data Polling Flow Chart

START

READ DQ5 & DQ7

at VALID ADDRESS

YES

DQ7

DATA7

DQ5

DQ7

DATA

READ DQ7

FAIL

Program/Erase

Operation Failed

Issue Reset Instruction

PASS

Program/Erase

Operation is

Completed

The

PSD935G2

Functional

Blocks

(cont.)

9.1.1.7.2 Data Toggle

Checking the Data Toggle bit on DQ6 is a method of determining whether a Program or

Erase instruction is in progress or has completed. Figure 5 shows the Data Toggle

algorithm.

When the MCU issues a programming instruction, the embedded algorithm within the

PSD935G2 begins. The MCU then reads the location to be programmed in Flash to check

status. Data bit DQ6 of this location will toggle each time the MCU reads this location until

the embedded algorithm is complete. The MCU continues to read this location, checking

DQ6 and monitoring the Error bit on DQ5. When DQ6 stops toggling (two consecutive

reads yield the same value), and the Error bit on DQ5 remains ‘0’, then the embedded

algorithm is complete. If the Error bit on DQ5 is ‘1’, the MCU should test DQ6 again, since

DQ6 may have changed simultaneously with DQ5 (see Figure 5).

The Error bit at DQ5 will be 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’).

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