ht82k94e Holtek Semiconductor Inc., ht82k94e Datasheet - Page 17

• Manufacturer Part Number: ht82k94e
• Description: Ht82k94e/ht82k94a -- Usb Multimedia Keyboard Encoder 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

optioned as CMOS/NMOS/PMOS configurations.
These control registers are mapped to locations 13H,
15H, 17H and 19H.
After a chip reset, these input/output lines remain at high
levels or floating state (depending on the pull-high op-
tions). Each bit of these input/output latches can be set
or cleared by SET [m].i and CLR [m].i (m=12H, 14H,
16H or 18H) instructions.
Some instructions first input data and then follow the
output operations. For example, SET [m].i , CLR
[m].i , CPL [m] , CPLA [m] read the entire port states
into the CPU, execute the defined operations
(bit-operation), and then write the results back to the
latches or the accumulator.
Each line of all the I/O ports have the capability of wak-
ing up the device.
There are pull-high options available for I/O lines. Once
the pull-high option of an I/O line is selected, the I/O line
have pull-high resistor. Otherwise, the pull-high resistor
is absent. It should be noted that a non-pull-high I/O line
operating in input mode will cause a floating state.
It is recommended that unused or not bonded out I/O
lines should be set as output pins by software instruction
to avoid consuming power under input floating state.
Low Voltage Reset/Detector - LVR/LVD
The microcontroller contains a low voltage reset circuit
in order to monitor the supply voltage of the device. If the
supply voltage of the device drops to within a range of
0.9V~V
tery, the LVR will automatically reset the device inter-
nally.
Note:
Rev. 1.90
LVR
*1. To make sure that the system oscillator has stabilized, the SST provides an extra delay of 1024 system
*2. Since low voltage has to be maintained for over 1ms in its original state, therefore there s a 1ms delay
such as might occur when changing the bat-
clock pulses before entering the normal operation.
before entering the reset mode
Low Voltage Reset
17
The LVR includes the following specifications:
The relationship between V
Note:
There is a low voltage detector (LVD) and a low voltage
reset circuit (LVR) implemented in the microcontrollers.
Where LVR function can be enabled/disabled by op-
tions. User can read the LVD detector status (0/1) from
MISC.5. The LVR has the same effect or function with
the external RES signal which performs a chip reset.
Both LVR and LVD functions will disable in the HALT
mode.
There are two kind of LVR/LVD definition: 2-battery or
3-battery option.
When 2-battery option is selected: LVR=2.2V;
LVD=2.4V. Otherwise, 3-battery option is selected:
LVR=2.4V; LVD=2.6V.
For a valid LVR signal, a low voltage i.e. a voltage in
the range between 0.9V~V
than 1ms. If the low voltage state does not exceed
1ms, the LVR will ignore it and do not perform a reset
function.
The LVR uses the OR function with the external
RES signal to perform chip reset.
V
tion at 4MHz system clock.
OPR
is the voltage range for proper chip opera-
HT82K94E/HT82K94A
DD
LVR
and V
must exist for greater
LVR
is shown below.
April 29, 2008