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參數資料
| 型號： | FM31256-S |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Integrated Processor Companion with Memory |
| 中文描述： | 綜合處理器與記憶體伴侶 |
| 文件頁數： | 5/22頁 |
| 文件大小： | 286K |
| 代理商： | FM31256-S |
The watchdog timer can also be used to assert the
reset signal (/RST). The watchdog is a free running
programmable timer. The period can be software
programmed from 100 ms to 3 seconds in 100 ms
increments via a 5-bit nonvolatile register. All
programmed settings are minimum values and vary
with temperature according to the operating
specifications. The watchdog has two additional
controls associated with its operation, a watchdog
enable bit (WDE) and timer restart bits (WR). Both
the enable bit must be set and the watchdog must
timeout in order to drive /RST active. If a reset event
occurs, the timer will automatically restart on the
rising edge of the reset pulse. If not enabled, the
watchdog timer runs but has no effect on /RST. Note
that setting the maximum timeout setting (11111b)
disables the counter to save power. The second
control is a nibble that restarts the timer preventing a
reset. The timer should be restarted after changing the
timeout value.
The watchdog timeout value is located in register
0Ah, bits 4-0, and the watchdog enable is bit 7. The
watchdog is restarted by writing the pattern 1010b to
the lower nibble of register 09h. Writing this pattern
will also cause the timer to load new timeout values.
Writing other patterns to this address will not affect
its operation. Note the watchdog timer is free-
running. Prior to enabling it, users should restart the
timer as described above. This assures that the full
timeout period will be set immediately after enabling.
The watchdog is disabled when V
DD
is below V
TP
.
The following table summarizes the watchdog bits. A
block diagram follows.
Watchdog timeout
WDT4-0
Watchdog enable
WDE
Watchdog restart
WR3-0
FM3104/16/64/256
Rev 0.2
May 2003
Page 5 of 22
0Ah, bits 4-0
0Ah, bit 7
09h, bits 3-0
Figure 3. Watchdog Timer
Manual Reset
The /RST pin is bi-directional and allows the
FM31xxx to filter and de-bounce a manual reset
switch. The /RST input detects an external low
condition and responds by driving the /RST signal
low for 100 ms.
Figure 4. Manual Reset
Note that an internal weak pull-up on /RST
eliminates
the
need
for
components.
additional
external
Reset Flags
In case of a reset condition, a flag will be set to
indicate the source of the reset. A low V
DD
reset is
indicated by the POR flag, register 09h bit 6. A
watchdog reset is indicated by the WTR flag, register
09h bit 7. A manual reset will result in no flag being
set, so the absence of a flag is a manual reset. Note
that the flags are internally set in response to reset
sources, but they must be cleared by the user. When
the register is read, it is possible that both flags are
set if both have occurred since the user last cleared
them.
Early Power Fail Comparator
An early power fail warning can be provided to the
processor well before V
DD
drops out of spec. The
comparator is used to create a power fail interrupt
(NMI). This can be accomplished by connecting the
PFI pin to the unregulated power supply via a resistor
divider. An application circuit is shown below. The
voltage on the PFI input pin is compared to an
onboard 1.2V reference. When the PFI input voltage
drops below this threshold, the comparator will drive
the CAL/PFO pin to a low state. The comparator has
300 mV (nominal) of hysteresis to reduce noise
sensitivity.
Figure 5. Comparator as Early Power-Fail Warning
+
-
1.2V ref
Regulator
VDD
FM31xxx
To MCU
NMI input
CAL/PFO
PFI
Timebase
Counter
Watchdog
timeout
100 ms
clock
WDE
/RST
WR3-0
= 1010b to restart
FM31xxx
Reset
Switch
RST
MCU
Switch
Behavior
RST
FM31xxx
drives
100 ms
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相關代理商/技術參數 |
參數描述 |
|---|---|
| FM31256-STR | 功能描述:監控電路 256K w/RTC Pwr Mon WDT Bat Sw PF RoHS:否 制造商:STMicroelectronics 監測電壓數: 監測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| FM31272 | 制造商:RAMTRON 制造商全稱:RAMTRON 功能描述:5V Integrated Processor Companion with Memory |
| FM31272-G | 功能描述:F-RAM 4K w/RTC Pwr Mon WDT Bat Sw PF RoHS:否 存儲容量:512 Kbit 組織:64 K x 8 接口:SPI 工作電源電壓:2 V to 3.6 V 工作溫度范圍:- 40 C to + 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube 制造商:Cypress Semiconductor |
| FM31272-GTR | 功能描述:F-RAM 4K w/RTC Pwr Mon WDT Bat Sw PF RoHS:否 存儲容量:512 Kbit 組織:64 K x 8 接口:SPI 工作電源電壓:2 V to 3.6 V 工作溫度范圍:- 40 C to + 85 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube 制造商:Cypress Semiconductor |
| FM31274 | 制造商:RAMTRON 制造商全稱:RAMTRON 功能描述:5V Integrated Processor Companion with Memory |
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