psd813f1a-90ut STMicroelectronics, psd813f1a-90ut Datasheet - Page 27

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

26
PSD913F1
The
PSD913F1
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 6 shows the Data Toggle
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 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 6).
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 Toggle method after an erase instructin, Figure 6 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 will generate ANSI C code functions which implement these Data Toggling
algorithms.
Figure 6. Data Toggle Flow Chart
NO
DQ5 & DQ6
READ DQ6
TOGGLE
TOGGLE
START
READ
DQ6
DQ5
DQ6
FAIL
=1
=
=
YES
YES
YES
NO
NO
PASS
Preliminary