PSD813F1 datasheet(29/120 Pages) STMICROELECTRONICS

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Preliminary

PSD813F1-A

The

PSD813F1

Functional

Blocks

(cont.)

9.1.1.7.1 Data Polling

Polling on DQ7 is a method of checking whether a Program or Erase instruction is in

progress or has completed. Figure 5 shows the Data Polling algorithm.

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

PSD813F1 begins. The MCU then reads the location of the byte to be programmed in Flash

to check status. Data bit DQ7 of this location becomes the compliment of data bit 7of the

original data byte to be programmed. The MCU continues to poll this location, comparing

DQ7 and monitoring the Error bit on DQ5. When the DQ7 matches data bit 7 of the original

data, and the Error bit at DQ5 remains ‘0’, then the embedded algorithm is complete.

If the Error bit at DQ5 is ‘1’, the MCU should test DQ7 again since DQ7 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 the byte 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 byte that was written to Flash with

the byte that was intended to be written.

When using the Data Polling method after an erase instruction, Figure 5 still applies.

However, DQ7 will be ‘0’ 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 DQ7 and DQ5.

PSDsoft will generate ANSI C code functions which implement these Data Polling

algorithms.

Figure 5. Data Polling Flow Chart

START

READ DQ5 & DQ7

at VALID ADDRESS

YES

DQ7

DATA7

DQ5

DQ7

DATA

READ DQ7

FAIL

PASS

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