HT82K95E/HT82K95A

Rev. 2.40

17

November 5, 2014

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

tery, the LVR will automatically reset the device inter-

nally.

The LVR includes the following specifications:

than 1ms. If the low voltage state does not exceed

1ms, the LVR will ignore it and do not perform a reset

function.

²OR² function with the external

RES signal to perform chip reset.

tion at 4MHz system clock.

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

²1² and a

USB interrupt is triggered to indicate that the

HT82K95E/HT82K95A should jump to the suspend

state to meet the 500

mA USB suspend current spec.

In order to meet the 500

mA suspend current, the firm-

ware should disable the USB clock by clearing the

USBCKEN (bit3 of the SCC) to

²0². The suspend cur-

rent is 400

mA.

User can further decrease the suspend current to 250

mA

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

²1² 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

²0². 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.

5 . 5 V

3 . 3 V

3 . 0 V

0 . 9 V

5 . 5 V

5 . 5 V

0 . 9 V

0 V

R e s e t S i g n a l

R e s e t

* 1

* 2

N o r m a l O p e r a t i o n

R e s e t

L V R D e t e c t V o l t a g e

Low Voltage Reset

Note: *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 low voltage has to be maintained for over 1ms in its original state, therefore there

¢s a 1ms delay

before entering the reset mode