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參數(shù)資料
| 型號(hào)： | P87C54 |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | 80C51 8-bit microcontroller family 8K.64K/256.1K OTP/ROM/ROMless, low voltage 2.7V.5.5V, low power, high speed 33 MHz |
| 中文描述： | 80C51的8位單片機(jī)系列8K.64K/256.1K檢察官辦公室/光盤/無ROM，2.7V.5.5V低電壓，低功耗，高速33兆赫 |
| 文件頁數(shù)： | 31/56頁 |
| 文件大小： | 360K |
| 代理商： | P87C54 |
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Philips Semiconductors
Product specification
8XC54/58
8XC51FA/FB/FC/80C51FA
8XC51RA+/RB+/RC+/RD+/80C51RA+
80C51 8-bit microcontroller family
8K–64K/256–1K OTP/ROM/ROMless, low voltage (2.7V–5.5V),
low power, high speed (33MHz)
2000 Aug 07
31
(8XC51FX and 8XC51RX+ ONLY)
––
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMn
ECCFn
CCAPM4
(DEH)
CH
CL
CCAP4H
CCAP4L
RESET
PCA TIMER/COUNTER
X
0
0
0
16–BIT COMPARATOR
MATCH
ENABLE
WRITE TO
CCAP4H
RESET
WRITE TO
CCAP4L
0
1
1
CMOD
(D9H)
CIDL
WDTE
––
––
––
CPS1
CPS0
ECF
X
SU00832
MODULE 4
Figure 25. PCA Watchdog Timer m(Module 4 only)
PCA Watchdog Timer
An on-board watchdog timer is available with the PCA to improve
the reliability of the system without increasing chip count. Watchdog
timers are useful for systems that are susceptible to noise, power
glitches, or electrostatic discharge. Module 4 is the only PCA
module that can be programmed as a watchdog. However, this
module can still be used for other modes if the watchdog is not
needed.
Figure 25 shows a diagram of how the watchdog works. The user
pre-loads a 16-bit value in the compare registers. Just like the other
compare modes, this 16-bit value is compared to the PCA timer
value. If a match is allowed to occur, an internal reset will be
generated. This will not cause the RST pin to be driven high.
In order to hold off the reset, the user has three options:
1. periodically change the compare value so it will never match the
PCA timer,
2. periodically change the PCA timer value so it will never match
the compare values, or
3. disable the watchdog by clearing the WDTE bit before a match
occurs and then re-enable it.
The first two options are more reliable because the watchdog timer
is never disabled as in option #3. If the program counter ever goes
astray, a match will eventually occur and cause an internal reset.
The second option is also not recommended if other PCA modules
are being used. Remember, the PCA timer is the time base for
all
modules; changing the time base for other modules would not be a
good idea. Thus, in most applications the first solution is the best
option.
Figure 26 shows the code for initializing the watchdog timer.
Module 4 can be configured in either compare mode, and the WDTE
bit in CMOD must also be set. The user’s software then must
periodically change (CCAP4H,CCAP4L) to keep a match from
occurring with the PCA timer (CH,CL). This code is given in the
WATCHDOG routine in Figure 26.
This routine should not be part of an interrupt service routine,
because if the program counter goes astray and gets stuck in an
infinite loop, interrupts will still be serviced and the watchdog will
keep getting reset. Thus, the purpose of the watchdog would be
defeated. Instead, call this subroutine from the main program within
2
16
count of the PCA timer.
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| P87C54SFPN | 80C51 8-bit microcontroller family 8K.64K/256.1K OTP/ROM/ROMless, low voltage 2.7V.5.5V, low power, high speed 33 MHz |
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| P87C54EBPN | IC |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| P87C541 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| P87C54-1 | 制造商:INTEL 制造商全稱:Intel Corporation 功能描述:CHMOS SINGLE-CHIP 8-BIT MICROCONTROLLER |
| P87C541 S F76 | 制造商:Intel 功能描述:MCU 8-bit MCS51 8051 CISC 16KB EPROM 5V 40-Pin PDIP |
| P87C54-2 | 制造商:INTEL 制造商全稱:Intel Corporation 功能描述:CHMOS SINGLE-CHIP 8-BIT MICROCONTROLLER |
| P87C54-20 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-Bit Microcontroller |
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