Chapter7. Reset Function
CHAPTER 7. RESET FUNCTION
7.1 EXTERNAL RESET
The RESET pin should be held at low for at least 2machine cycles with the power supply
voltage within the operating voltage range and must be connected 0.1uF capacitor
for stable system initialization.
The RESET pin contains a Schmitt trigger with an internal pull-up resistor.
RESET
0.1uF capacitor
Fig 7.0 RESET Pin connection.
7.2 POWER ON RESET
Power On Reset circuit automatically detects the rise of power voltage (the rising time
should be within 50ms) the power voltage reaches a certain level, RESET terminal is
¡ È ¡ È
Level until a crystal ceramic oscillator oscillates stably. After power
maintained at
L
applies and starting of oscillation, this reset state is maintained for about oscillation cycle of
219 (about 65.5ms : at 4MHz).
The execution of built-in Power On Reset circuit is as follows :
(1) Latch the pulse from Power On Detection Pulse Generator circuit, and reset
Prescaler, B.I.T and B.I.T Overflow detection circuit.
(2) Once B.I.T Overflow detection circuit is reset. Then, Prescaler starts to count.
(3) Prescaler output is inputted into B.I.T and PS10 of Prescaler output is automatically
selected. If overflow of B.I.T is detected, Overflow detection circuit is set.
(4) Reset circuit generates maximum period of reset pulse from Prescaler and B.I.T.
7 - 1
HYNIX [ HYNIX SEMICONDUCTOR ]
