HT82B40A HOLTEK [Holtek Semiconductor Inc], HT82B40A Datasheet - Page 29

• Manufacturer Part Number: HT82B40A
• Description: I/O MCU with USB Interface
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Suspend Wake-Up and Remote Wake-Up
If there is no signal on the USB bus for over 3ms, the de-
vice will go into a suspend mode. The Suspend line (bit
0 of the USC register) will be set to 1 and a USB inter-
rupt is triggered to indicate that the devices 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 bit which is bit3 of the SCC register to 0 .
The suspend current is 400 A.
The user can further decrease the suspend current to
250 A by setting the SUSP2 bit which is bit4 of the SCC
register. If in the USB mode set this bit LVR OPT must
disable.
When the resume signal is sent out by the host, the de-
vices will wake up the MCU with a USB interrupt and the
Resume line (bit 3 of the USC register) is set. In order to
make the device function properly, the firmware must
set the USBCKEN (bit 3 of the SCC register) to 1 and
clear the SUSP2 (bit4 of the SCC register). 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
register) will be set to 0 . So when the MCU is detecting
the Suspend line (bit0 of USC register), the Resume line
condition should be noted and taken into consideration.
After finishing the resume signal, the suspend line will
go inactive and a USB interrupt will be triggered. The fol-
lowing is the timing diagram.
As the device has a remote wake up function it can
wake-up the USB Host by sending a wake-up pulse
through RMWK (bit 1 of the USC register). Once the
USB Host receives a wake-up signal from the devices, it
will send a Resume signal to the device. The timing is as
follows:
Rev. 1.10
29
To Configure as PS2 Device
The devices can also be configured as a USB interface
or PS2 interface device, by configuring SPS2 (bit 4 of
the USR register) and SUSB (bit 5 of the USR register).
If SPS2=1, and SUSB=0, the device will be configured
as a PS2 interface, pin USBD- is configured as a PS2
Data pin and USBD+ is configured as a PS2 Clk pin. The
user can read or write to the PS2 Data or PS2 Clk pin by
accessing the corresponding bit PS2DAI (bit 4 of the
USC register), PS2CKI (bit 5 of the USC register),
PS2DAO (bit 6 of the USC register) and S2CKO (bit 7 of
the USC register) respectively.
The user should make sure that in order to read the data
properly, the corresponding output bit must be set to 1 .
For example, if it is desired to read the PS2 Data by
reading PS2DAI, then PS2DAO should set to 1 . Oth-
erwise it is always read as 0 .
If SPS2=0, and SUSB=1, the device is configured as a
USB interface. Both the USBD- and USBD+ is driven by
the SIE of the HT82B40R/ HT82B40A . The user can
only write or read the USB data through the correspond-
ing FIFO. Both the SPS2 and SUSB default is 0 .
USB Interface
There are eleven registers used for the USB function.
The AWR register contains the current address and a
remote wake up function control bit. The initial value of
AWR is 00H . The address value extracted from the
USB command is not to be loaded into this register until
the SETUP stage is completed.
Bit No.
7~1
0
AD6~AD0
WKEN
Label
AWR (42H) Register
HT82B40R/HT82B40A
R/W
W
W
Remote wake-up
enable/disable
USB device address
September 4, 2009
Function