100m
10m
1m
100
10
µ
µ
µ
1
trise (seconds)
1
10 100 1m 10m 100m
µ µ µ
Power-voltage activation time
Fig. 3 EEPROM initialization time
When the power-on clear circuit has finished initialization normally, the EEPROM enters a program-
disabled state. If the power-on clear circuit does not operate, the following situation is likely:
-
In some cases, a previously entered command has been enabled. If, for example, a program-
enabled command has been enabled and the input terminal mistakenly recognizes a write command
due to extraneous noise while the next command is being entered, writing may be executed.
The following may prevent the power-on clear circuit from operating:
-
If the power lines of the microcomputer and EEPROM are separated from each other, and the output
terminals of the microcomputer and EEPROM are wired or connected to each other, there may be a
potential difference between the power lines of the EEPROM and microcomputer. If the voltage of
the microcomputer is higher, a current may flow from the output terminal of the microcomputer to the
power line of the EEPROM via a parasitic diode in the DO pin of the EEPROM. Therefore, the power
voltage of the EEPROM has an intermediate potential to prevent power-on from being cleared.
-
During an access to the EEPROM, the voltage may decrease due to power-off. Even if the
microcomputer has been reset due to a decrease in voltage, the EEPROM may malfunction if
EEPROM power-on clear operation conditions are not met. For the EEPROM power-on clear
operation conditions, see “Method for Activating the Power Voltage.”
<Remarks>
FAQ No.: 12011
38
SII [ SEIKO INSTRUMENTS INC ]
