PSD813F1 datasheet(28/110 Pages) STMICROELECTRONICS

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PSD813F1

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Data Toggle

Checking the Data Toggle bit on DQ6 is a method

of determining whether a Program or Erase in-

struction is in progress or has completed. Figure

10 shows the Data Toggle algorithm.

When the MCU issues a programming instruction,

the embedded algorithm within the PSD begins.

The MCU then reads the location of the byte 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 loca-

tion, 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

10).

The Error bit at DQ5 will be set if either an internal

timeout occurred while the embedded algorithm

attempted to program the byte, or if the MCU at-

tempted 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 program-

ming algorithm has completed to compare the byte

that was written to Flash with the byte that was in-

tended to be written.

When using the Data Toggle method after an

erase instruction, Figure 10 still applies. DQ6 will

toggle until the erase operation is complete. A ‘1’

on DQ5 will indicate a timeout failure of the erase

operation, a ‘0’ indicates no error. The MCU can

read any location within the sector being erased to

get DQ6 and DQ5.

PSDsoft Express will generate ANSI C code func-

tions which implement these Data Toggling algo-

rithms.

Figure 10. Data Toggle Flowchart

READ

DQ5 & DQ6

START

READ DQ6

FAIL

PASS

AI01370B

DQ6

TOGGLE

YES

DQ5

= 1

YES

DQ6

TOGGLE

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