psd813f1a-90ut STMicroelectronics, psd813f1a-90ut Datasheet - Page 26

• Manufacturer Part Number: psd813f1a-90ut
• Description: Flash In-system Programmable Isp Peripherals For 8-bit Mcus
• Manufacturer: STMicroelectronics

Preliminary
The
PSD913F1
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
PSD913F1 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
NO
at VALID ADDRESS
READ DQ5 & DQ7
READ DQ7
DATA7
START
DATA
DQ7
DQ5
FAIL
DQ7
=
=1
=
YES
NO
NO
YES
YES
PASS
PSD913F1
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