HT48CA0 Datasheet, PDF (14/36 Pages) Holtek Semiconductor Inc – 8-bit Microcontroller

HT48CA0
Low voltage reset — LVR
The HT48CA0 provides low voltage reset circuit
in order to monitor the supply voltage of the
device. If the supply voltage of the device is
within the range 0.9V~2.2V, such as changing a
battery, the LVR will automatically reset the
device internally.
The LVR includes the following specifications:
• _{The low voltage (0.9V~2.2V) has to remain in}
their original state to exceed 1 ms. If the low
voltage state does not exceed 1 ms, the LVR
will ignore it and do not perform a reset func-
tion.
• _{The LVR uses the “OR” function with the exter-}
nal RES signal to perform chip reset.
• _{During HALT mode, if the LVR occurs, the}
device will wake-up and the PD flag will be set
as “1”, the same as the external RES.
Because the operating voltage (VDD) is
2.2V~3.6V and the LVR operating voltage
(VLVR) is 0.9V~2.2V, therefore one margin volt-
age about 0.1V is needed for proper chip opera-
tion. The relationship between VDD and VLVR is
shown below.
Note: VOPR is the voltage range for proper chip
operation at 4MHz system clock.
Carrier
The HT48CA0 provides a carrier output which
shares the pin with PC0. It can be selected to be
a carrier output (REM) or level output pin (PC0)
by mask option. If the carrier output option is
selected, setting PC0=“0” to enable carrier out-
put and setting PC0=“1” to disable it at low
level output.
Low voltage reset
*1: To make sure that the system oscillator has stabilized, the SST provides an extra delay of 1024
system clock pulses before entering the normal operation.
*2: Since the low voltage has to maintain in its original state and exceed 1 ms, therefore 1 ms delay
is needed to enter the reset mode.
14
23rd July ’98