ht82a821r Holtek Semiconductor Inc., ht82a821r Datasheet - Page 17

• Manufacturer Part Number: ht82a821r
• Description: Ht82a821r -- Usb Audio Mcu
• Manufacturer: Holtek Semiconductor Inc.

There is a system clock control register implemented to select the clock used in the MCU. This register consists of USB
clock control bit (USBCKEN), second suspend mode control bit (SUSP2) and system clock selection (SYSCLK)
And to define which endpoint FIFO is select by EPS2, EPS1 and EPS0.
Note: Isochronous endpoint 2 is implemented by hardware, so FIFO2 can not read/write by firmware.
AWR register contains 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 has not to be loaded into this register until the SETUP stage be-
ing finished.
STALL register shows where the corresponding endpoint works properly or not. As soon as the endpoint works improp-
erly, the related bit in the STALL has to be set to 1 . The STALL will be cleared by USB reset signal.
Rev. 1.10
Bit No.
Bit No.
Bit No.
0~2
1~7
0~2
3~7
3
4
5
6
0
EPS0~EPS2
STL0~STL2
STL3~STL7
f
USBCKEN
SYS
AD0~AD6
SYSCLK
SUSP2
WKEN
Label
Label
Label
24MHz
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Power-on
Power-on
Reset
0
0
0
0
0
0
0
0
0
STALL (24H) Register
AWR (23H) Register
UCC (22H) Register
Accessing endpoint FIFO selection, EPS2, EPS1, EPS0:
000: Select endpoint 0 FIFO
001: Select endpoint 1 FIFO
010: Select endpoint 2 FIFO
011: reserved for future expansion, cannot be used
100: reserved for future expansion, cannot be used
101: reserved for future expansion, cannot be used
110: reserved for future expansion, cannot be used
111: reserved for future expansion, cannot be used
If the selected endpoints are not existed, the related functions will be
absent.
USB clock control bit. When this bit is set to 1 , it indicates that the
USB clock is enabled.
Otherwise, the USB clock is turned-off.
This bit is used for reducing power consumption in suspend mode.
In normal mode, clean this bit to 0
In HALT mode, set this bit to 1 for reducing power consumption.
This bit is used to define the MCU system clock comes form external
OSC or system clock comes PLL output 24MHz clock.
0: system clock comes from OSC
1: system clock comes from PLL output 24MHz
This bit is used to specify the system clock oscillator frequency used
by MCU.
If a 6MHz crystal oscillator or resonator is used, this bit should be set
to 1 .
If a 12MHz crystal oscillator or resonator is used. this bit should be
cleared to 0 .
USB remote-wake-up enable/disable (1/0)
USB device address
Set by users when related USB endpoints were stalled. They are
cleared by USB reset and Setup Token event.
Undefined bit, read as 0 .
17
Functions
Functions
Functions
HT82A821R
June 29, 2007