參數(shù)資料
型號(hào)： P83C661X2BBD
廠商： NXP SEMICONDUCTORS
元件分類： 微控制器/微處理器
英文描述： 80C51 8-bit microcontroller family
中文描述： 8-BIT, MROM, 33 MHz, MICROCONTROLLER, PQFP44
封裝： 10 X 10 MM, 1.40 MM HEIGHT, PLASTIC, MS-026, SOT-389-1, LQFP-44
文件頁數(shù)： 73/102頁
文件大?。?/td> 584K
代理商： P83C661X2BBD
Philips Semiconductors
Product data
P8xC660X2/661X2
80C51 8-bit microcontroller family
16 KB OTP/ROM, 512B
RAM, low voltage (2.7 to 5.5 V), low power, high speed (30/33
MHz), two 400KB I
2
C interfaces
2003 Oct 02
73
––
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
CCAP4L
RESET
WRITE TO
CCAP4H
1
0
1
CMOD
(D9H)
CIDL
WDTE
––
––
––
CPS1
CPS0
ECF
X
SU01612
MODULE 4
Figure 46. PCA Watchdog Timer mode (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 46 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 47 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 47.
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.
相關(guān)PDF資料
PDF描述
P83C661X2FA 80C51 8-bit microcontroller family
P83C661X2 80C51 8-bit microcontroller family 16KB OTP/ROM. 512B RAM low voltage (2.7 to 5.5 V). low power. high speed (30/33 MHZ). two 400KB I2C interfaces
P83C660X2 80C51 8-bit microcontroller family 16KB OTP/ROM. 512B RAM low voltage (2.7 to 5.5 V). low power. high speed (30/33 MHZ). two 400KB I2C interfaces
P87C660X2 80C51 8-bit microcontroller family 16KB OTP/ROM. 512B RAM low voltage (2.7 to 5.5 V). low power. high speed (30/33 MHZ). two 400KB I2C interfaces
P87C661X2 80C51 8-bit microcontroller family 16KB OTP/ROM. 512B RAM low voltage (2.7 to 5.5 V). low power. high speed (30/33 MHZ). two 400KB I2C interfaces
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