ht82k95e Holtek Semiconductor Inc., ht82k95e Datasheet - Page 17

• Manufacturer Part Number: ht82k95e
• Description: Ht82k95e/ht82k95a -- Usb Multimedia Keyboard Encoder 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

Low Voltage Reset - LVR
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.
The LVR includes the following specifications:
The relationship between V
Note: V
Note: *1. To make sure that the system oscillator has stabilized, the SST provides an extra delay of 1024 system
Rev. 2.00
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.
tion at 4MHz system clock.
*2. Since low voltage has to be maintained for over 1ms in its original state, therefore there s a 1ms delay
LVR
OPR
before entering the reset mode
clock pulses before entering the normal operation.
such as might occur when changing the bat-
is the voltage range for proper chip opera-
DD
LVR
and V
must exist for greater
LVR
is shown below.
Low Voltage Reset
17
Suspend Wake-Up and Remote Wake-Up
If there is no signal on the USB bus for over 3ms, the
HT82K95E/HT82K95A will go into suspend mode. The
Suspend line (bit 0 of the USC) will be set to 1 and a
USB interrupt is triggered to indicate that the
HT82K95E/HT82K95A should jump to the suspend
state to meet the 500 A USB suspend current spec.
In order to meet the 500 A suspend current, the firm-
ware should disable the USB clock by clearing the
USBCKEN (bit3 of the SCC) to 0 . The suspend cur-
rent is 400 A.
User can further decrease the suspend current to 250 A
by setting the SUSP2 (bit4 of the SCC). If in USB mode
set this bit LVR OPT must disable
When the resume signal is sent out by the host, the
HT82K95E/HT82K95A will wake up the MCU by USB in-
terrupt and the Resume line (bit 3 of the USC) is set. In
order to make the HT82K95E/HT82K95A function prop-
erly, the firmware must set the USBCKEN (bit 3 of the
SCC) to 1 and clear the SUSP2 (bit4 of the SCC).
Since the Resume signal will be cleared before the Idle
signal is sent out by the host, the Suspend line (bit 0 of
the USC) will be set to 0 . So when the MCU is detect-
ing the Suspend line (bit0 of USC), the Resume line
should be remembered and taken into consideration.
After finishing the resume signal, the suspend line will
go inactive and a USB interrupt is triggered. The follow-
ing is the timing diagram.
HT82K95E/HT82K95A
April 16, 2008