參數(shù)資料
型號： PXAS31KFA
廠商： NXP SEMICONDUCTORS
元件分類： 微控制器/微處理器
英文描述： XA 16-bit microcontroller 32K/1K OTP/ROM/ROMless, 8-channel 8-bit A/D, low voltage 2.7 V.5.5 V, I2C, 2 UARTs, 16MB address range
中文描述： 16-BIT, OTPROM, 30 MHz, MICROCONTROLLER, PQCC68
封裝： PEDESTAL, PLASTIC, MO-047AE, SOT-188-3, LCC-68
文件頁數(shù)： 26/52頁
文件大小： 281K
代理商： PXAS31KFA
Philips Semiconductors
XA 16-bit microcontroller
32K/1K OTP/ROM/ROMless, 8-channel 8-bit A/D, low voltage (2.7 V–5.5 V),
I
2
C, 2 UARTs, 16 MB address range
Preliminary specification
XA-S3
2000 Mar 09
26
––
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMn
ECCFn
CCAPM4
(495H)
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
(490H)
CIDL
WDTE
––
––
––
CPS1
CPS0
ECF
X
SU01313
MODULE 4
Figure 18. 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 18 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 low.
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 19 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 19.
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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PXAS31KFBE 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:XA 16-bit microcontroller 32K/1K OTP/ROM/ROMless, 8-channel 8-bit A/D, low voltage 2.7 V.5.5 V, I2C, 2 UARTs, 16MB address range
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PXAS33KBBE 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:XA 16-bit microcontroller 32K/1K OTP/ROM/ROMless, 8-channel 8-bit A/D, low voltage 2.7 V.5.5 V, I2C, 2 UARTs, 16MB address range
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