impact it,measure the voltage between 13 pin and 16 pin.If the voltage is lower than 4V,take the
RT809F apart first,find two 302 resistors(3k),R63 and R64,and change them to 102 resistor(1k).The
RT809F produced after Dec. 2013 has changed the R63/R64 to 1k resistor,so do not need to
change anymore.But if the resistor is 1k,the voltage between 13 pin and 16 pin is still low,please
remove the 78L05 of the ICSP port board(Useful for PIC series,not for S3F series);
Connect the S3F chip with the ICSP port board using the line first and then put on the locking
socket;according to the practical testing,please be attention that GND ground line must be
connected correctly or it will breakdown between the VPP and VDD pin of the MCU to damage the
chip when begin to read or write without connecting well.(Use the numeration table diode to test
MCU,red probe connects VPP pin,black probe connects VDD pin,the value is infinity normally,after
breakdown the value is 500 and more.)
The solving method : Series connect a Schottky diode on the VDD line,such as 1N5819,SS14 and
other types,connect the positive pole to one side of the ICSP port board,connect the negative pole
to the side with VDD pin of MCU,which can avoid the problem that the VPP pin break down the
VDD pin because of connecting the GND ground line poorly.
According to chip DATASHEET,if just need to read MCU but not write,then connect the VPP pin of
MCU to VDD directly but not to 12.5V.However according to the actual test,when reading
S3F9498/S3F9488 with VPP pin connecting with VDD pin,verifying will fail after reading chip;but if
connect VPP pin to 12.5 instead and read,verifying will pass.
S3F series MCU,if VPP and nRST are at the same pin,like S3F9454,after charging the VDD/VPP
it’s allowed to read or verify in 200ms;and if they are not at the same pin like S3F9498,it has no
limit for the timing sequence;
It comes with a problem : If the configuration of some computer hardware is low,or with a slow
system,which result in the failure to read or write the S3F9454 again and again,so that to think the
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