參數(shù)資料
型號(hào)： HT82A821R
廠商： Holtek Semiconductor Inc.
英文描述： USB Audio MCU
中文描述： USB音頻控制器
文件頁(yè)數(shù)： 11/39頁(yè)
文件大?。?/td> 275K
代理商： HT82A821R
HT82A821R
Rev. 1.10
11
June 29, 2007
Power Down Operation
HALT
The HALT mode is initialized by the HALT instruction
and results in the following:
The system oscillator will be turned off but the WDT
oscillator remains running (if the WDT oscillator is se-
lected).
The contents of the on-chip RAM and registers remain
unchanged.
The WDT and WDT prescaler will be cleared and re-
counted again (if the WDT clock is from the WDT os-
cillator).
All of the I/O ports remain in their original status.
The PDF flag is set and the TO flag is cleared.
The system can leave the HALT mode by means of an
external reset, an interrupt, an external falling edge sig-
nal on port A or a WDT overflow. An external reset
causes a device initialization and the WDToverflow per-
forms a warm reset . After the TO and PDF flags are
examined, the cause for chip reset can be determined.
The PDF flag is cleared by a system power-up or exe-
cuting the CLR WDT instruction and is set when exe-
cuting the HALT instruction. The TO flag is set if the
WDT time-out occurs, and causes a wake-up that only
resets the program counter and SP; the others remain in
their original status.
The port A wake-up and interrupt methods can be con-
sidered as a continuation of normal execution. Each bit
in port A can be independently selected to wake-up the
devicebymaskoption.AwakeningfromanI/Oportstim-
ulus, the program will resume execution of the next in-
struction. If it awakens from an interrupt, two sequence
may occur. If the related interrupt is disabled or the inter-
rupt is enabled but the stack is full, the program will re-
sume execution at the next instruction. If the interrupt is
enabled and the stack is not full, the regular interrupt re-
sponse takes place. If an interrupt request flag is set to
1 before entering the HALT mode, the wake-up func-
tion of the related interrupt will be disabled. Once a
wake-up event occurs, it takes 1024 t
SYS
(system clock
period) to resume normal operation. In other words, a
dummy period will be inserted after a wake-up. If the
wake-up results from an interrupt acknowledge signal,
the actual interrupt subroutine execution will be delayed
by one or more cycles. If the wake-up results in the next
instruction execution, this will be executed immediately
after the dummy period is finished.
To minimize power consumption, all the I/O pins should
be carefully managed before entering the HALT status.
Reset
Therearefourwaysinwhicharesetcanoccur:
RES reset during normal operation
RES reset during HALT
WDT time-out reset during normal operation
USB reset
The WDT time-out during HALT is different from other
chip reset conditions, since it can perform a warm re -
set that resets only the program counter and SP, leav-
ing the other circuits in their original state. Some regis-
ters remain unchanged during other reset conditions.
Most registers are reset to the initial condition when
the reset conditions are met. By examining the PDF and
TO flags, the program can distinguish between different
chip resets .
TO PDF
RESET Conditions
0
0
RESET reset during power-up
u
u
RESET reset during normal operation
0
1
RESET wake-up HALT
1
u
WDT time-out during normal operation
1
1
WDT wake-up HALT
Note: u stands for unchanged
To guarantee that the system oscillator is started and
stabilized, the SST (System Start-up Timer) provides an
extra delay of 1024 system clock pulses when the sys-
tem resets (power-up, WDT time-out or RES reset) or
the system awakes from the HALT state.
When a system reset occurs, the SST delay is added
during the reset period. Any wake-up from HALT will en-
able the SST delay.
2
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Reset Circuit
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Reset Configuration
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Reset Timing Chart
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