HT82A821R_07 HOLTEK [Holtek Semiconductor Inc], HT82A821R_07 Datasheet - Page 15

• Manufacturer Part Number: HT82A821R_07
• Description: USB Audio MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Low Voltage Reset - LVR (by ROM Code Option)
The LVR option is 3.0V.
The microcontroller 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~V
tomatically reset the device internally.
The LVR includes the following specifications:
Suspend Wake-Up and Remote Wake-Up
If there is no signal on the USB bus for over 3ms, the
HT82A821R will go into a suspend mode. The Suspend
line (bit 0 of the USC) will be set to 1 and a USB inter-
rupt is triggered to indicate that the HT82A821R should
jump to the suspend state to meet the USB suspend cur-
rent spec.
In order to meet the suspend current, the firmware
should disable the USB clock by clearing the USBCKEN
(bit3 of the UCC) to 0 .
Also the user can further decrease the suspend current
by set the SUSP2 (bit4 of the UCC).
When the resume signal is sent out by the host, the
HT82A821R will wake up the MCU by USB interrupt and
Rev. 1.10
The low voltage (0.9V~V
original state to exceed 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
RESET signal to perform chip reset.
LVR
such as changing a battery, the LVR will au-
LVR
) has to remain in their
15
the Resume line (bit 3 of USC) is set. In order to make
HT82A821R work properly, the firmware must set the
USBCKEN (bit 3 of UCC) to 1 and clear the SUSP2 (bit4
of the UCC). Since the Resume signal will be cleared
before the Idle signal is sent out by the host and the Sus-
pend line (bit 0 of USC) is going to 0 . So when the
MCU is detecting the Suspend line (bit0 of USC), the
Resume line should be remembered and token into con-
sideration. The following is the timing diagram:
The device with remote wake up function can wake-up
the USB Host by sending a wake-up pulse through
RMWK (bit 1 of USC). Once the USB Host receive the
wake-up signal from HT82A821R, it will send a Resume
signal to device. The timing as follow:
HT82A821R
June 29, 2007