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參數(shù)資料
| 型號： | ST72T631K2M0 |
| 廠商： | 意法半導體 |
| 英文描述： | LOW SPEED USB 8-BIT MCU FAMILY with up to 16K MEMORY, up to 512 BYTES RAM, 8-BIT ADC, WDG, TIMER, SCI & I2C |
| 中文描述： | 低速USB 8高達16K的內(nèi)存位微控制器系列，高達512字節(jié)RAM，8位ADC，水分散粒劑，定時器，SCI |
| 文件頁數(shù)： | 34/109頁 |
| 文件大?。?/td> | 857K |
| 代理商： | ST72T631K2M0 |
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ST7263
34/109
WATCHDOG TIMER
(Cont’d)
5.3.3 Functional Description
The counter value stored in the CR register (bits
T6:T0), is decremented every 49,152 machine cy-
cles, and the length of the timeout period can be
programmed by the user in 64 increments.
If the watchdog is activated (the WDGA bit is set)
and when the 7-bit timer (bits T6:T0) rolls over
from 40h to 3Fh (T6 becomes cleared), it initiates
a reset cycle pulling low the reset pin for typically
500ns.
The application program must write in the CR reg-
ister at regular intervals during normal operation to
prevent an MCU reset. The value to be stored in
the CR register must be between FFh and C0h
(see
Table 14 . Watchdog Timing (fCPU = 8
MHz)
):
– The WDGA bit is set (watchdog enabled)
– The T6 bit is set to prevent generating an imme-
diate reset
– The T5:T0 bits contain the number of increments
which represents the time delay before the
watchdog produces a reset.
Table 14. Watchdog Timing (f
CPU
= 8 MHz)
Notes:
Following a reset, the watchdog is disa-
bled. Once activated it cannot be disabled, except
by a reset.
The T6 bit can be used to generate a software re-
set (the WDGA bit is set and the T6 bit is cleared).
5.3.3.1 Using Halt Mode with the WDG
The HALT instruction stops the oscillator. When
the oscillator is stopped, the WDG stops counting
and is no longer able to generate a reset until the
microcontroller receives an external interrupt or a
reset.
If an external interrupt is received, the WDG re-
starts counting after 4096 CPU clocks. If a reset is
generated, the WDG is disabled (reset state).
Recommendations
– Make sure that an external event is available to
wake up the microcontroller from Halt mode.
– Before executing the HALT instruction, refresh
the WDG counter, to avoid an unexpected WDG
reset immediately after waking up the microcon-
troller.
– When using an external interrupt to wake up the
microcontroller, reinitialize the corresponding I/O
as “Input Pull-up with Interrupt” before executing
the HALT instruction. The main reason for this is
that the I/O may be wrongly configured due to ex-
ternal interference or by an unforeseen logical
condition.
– For the same reason, reinitialize the level sensi-
tiveness of each external interrupt as a precau-
tionary measure.
– The opcode for the HALT instruction is 0x8E. To
avoid an unexpected HALT instruction due to a
program counter failure, it is advised to clear all
occurrences of the data value 0x8E from memo-
ry. For example, avoid defining a constant in
ROM with the value 0x8E.
– As the HALT instruction clears the I bit in the CC
register to allow interrupts, the user may choose
to clear all pending interrupt bits before execut-
ing the HALT instruction. This avoids entering
other peripheral interrupt routines after executing
the external interrupt routine corresponding to
the wake-up event (reset or external interrupt).
5.3.4 Interrupts
None.
5.3.5 Register Description
CONTROL REGISTER (CR)
Read/Write
Reset Value: 0111 1111 (7Fh)
Bit 7 =
WDGA
Activation bit
.
This bit is set by software and only cleared by
hardware after a reset. When WDGA = 1, the
watchdog can generate a reset.
0: Watchdog disabled
1: Watchdog enabled
Bit 6:0 =
T[6:0]
7-bit timer (MSB to LSB).
These bits contain the decremented value. A reset
is produced when it rolls over from 40h to 3Fh (T6
becomes cleared).
CR Register
initial value
FFh
C0h
WDG timeout period
(ms)
393.216
6.144
Max
Min
7
0
WDGA
T6
T5
T4
T3
T2
T1
T0
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ST72T631K4B1 | 功能描述:8位微控制器 -MCU OTP EPROM 16K USB/SC RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT |
| ST72T631K4M1 | 功能描述:8位微控制器 -MCU OTP EPROM 16K USB/SC RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT |
| ST72T631L4M1 | 制造商:STMicroelectronics 功能描述:8-BIT MICROCONTROLLER - Bulk |
| ST72T632K2B1 | 功能描述:8位微控制器 -MCU OTP EPROM 8K USB/SCI RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT |
| ST72T632K2M1 | 功能描述:8位微控制器 -MCU OTP EPROM 8K USB/SCI RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT |
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