鈥?/div>
Serial Programming at Voltages below 2.9 Volts
3. Releasing Reset Condition without Clock
If an external reset or a watchdog reset occurs while the clock is stopped and the
reset is released before the clock is restarted, the internal reset will time out after
the start-up delay, which is independent of the external clock. If no external clock
pulses are present in the period when internal reset is active, the reset does cor-
rectly cause tri-stating of the I/O while the reset is held. However, if the internal
reset is relesed before the clock starts running, the part does not clear its I/O reg-
isters, nor set PC to 0x00. Here, stopping the clock refers to gating the external
clock input. Power-down mode does not have this issue.
Problem Fix/Workaround
Make sure the clock is running whenever an external reset can be expected. If the
watchdog is used, never stop an external clock.
2. Reset during EEPROM Write
If reset is activated during EEPROM write, the result is not what should be
expected. The EEPROM write cycle completes as normal, but the address regis-
ters are reset to 0. The result is that both the address written and address 0 in the
EEPROM can be corrupted.
Problem Fix/Workaround
Avoid using address 0 for storage, unless you can guarantee that you will not get
a reset during EEPROM write.
1. Serial Programming at Voltages below 2.9 Volts
At voltages below 2.9 Volts, serial programming might fail.
Problem Fix/Workaround
Keep V
CC
at 2.9 Volts or higher during In-System Programming.
8-bit
Microcontroller
with 1K Byte
In-System
Programmable
Flash
AT90S1200/A
Rev. F
Errata Sheet
Rev. 1190D鈥?9/01
1
1
2
