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| 型号： | 7549 |
| 厂商： | Renesas Technology Corp. |
| 英文描述： | SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| 中文描述： | 单芯片8位CMOS微机 |
| 文件页数： | 57/73页 |
| 文件大小： | 1272K |
| 代理商： | 7549 |
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Rev.2.00
REJ03B0202-0200
Mar 05, 2007
Page 57 of 70
7549 Group
PRELIMINARY
Notice: This is not a final specification.
Some parametric limits are subject to change.
5. Setup for I/O ports
Setup I/O ports using hardware and software as follows:
<Hardware>
Connect a resistor of 100
or more to an I/O port in series.
<Software>
As for an input port, read data several times by a program
for checking whether input levels are equal or not.
As for an output port, since the output data may reverse
because of noise, rewrite data to its port latch at fixed
periods.
Rewrite data to direction registers and pull-up control
registers at fixed periods.
Fig 77. Setup for I/O ports
6. Providing of watchdog timer function by software
If a microcomputer runs away because of noise or others, it can
be detected by a software watchdog timer and the microcomputer
can be reset to normal operation. This is equal to or more
effective than program runaway detection by a hardware
watchdog timer. The following shows an example of a watchdog
timer provided by software.
In the following example, to reset a microcomputer to normal op-
eration, the main routine detects errors of the interrupt processing
routine and the interrupt processing routine detects errors of the
main routine.
This example assumes that interrupt processing is repeated mul-
tiple times in a single main routine processing.
<The main routine>
Assigns a single byte of RAM to a software watchdog
timer (SWDT) and writes the initial value N in the SWDT
once at each execution of the main routine. The initial
value N should satisfy the following condition:
N + 1
≥
(Counts of interrupt processing executed in each
main routine)
As the main routine execution cycle may change because
of an interrupt processing or others, the initial value N
should have a margin.
Watches the operation of the interrupt processing routine
by comparing the SWDT contents with counts of interrupt
processing after the initial value N has been set.
Detects that the interrupt processing routine has failed and
determines to branch to the program initialization routine
for recovery processing in the following case:
If the SWDT contents do not change after interrupt
processing.
<The interrupt processing routine>
Decrements the SWDT contents by 1 at each interrupt
processing.
Determines that the main routine operates normally when
the SWDT contents are reset to the initial value N at almost
fixed cycles (at the fixed interrupt processing count).
Detects that the main routine has failed and determines to
branch to the program initialization routine for recovery
processing in the following case:
If the SWDT contents are not initialized to the initial value
N but continued to decrement and if they reach 0 or less.
Fig 78. Watchdog timer by software
N.G.
O.K.
Noise
Noise
Data bus
Direction register
Port latch
I/O port
pins
≠
N
N
>0
≤
0
Main routine
(SWDT)
←
N
CLI
Main processing
(SWDT)
=N
Interrupt processing
routine errors
Interrupt processing routine
(SWDT)
←
(SWDT)
1
Interrupt processing
(SWDT)
≤
0
RTI
Return
Main routine
errors
相关PDF资料 |
PDF描述 |
|---|---|
| 75HQ | SCHOTTKY RECTIFIER |
| 75HQ030 | SCHOTTKY RECTIFIER |
| 75HQ035 | SCHOTTKY RECTIFIER |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 7549_0710 | 制造商:RENESAS 制造商全称:Renesas Technology Corp 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| 7549_09 | 制造商:RENESAS 制造商全称:Renesas Technology Corp 功能描述:SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER |
| 7-5-4905 | 功能描述:3M 4905 VHB TAPE SPECIALTY TAPES 制造商:3m (tc) 系列:VHB?? 4905 零件状态:在售 厚度 - 粘合剂:- 厚度 - 底布，载体:- 标准包装:1 |
| 754905-1 | 功能描述:PIN ATT/ROLL AUTO IV 制造商:te connectivity amp connectors 系列:* 零件状态:有效 标准包装:1 |
| 7-5-4910 | 功能描述:3M 4910 VHB TAPE SPECIALTY TAPES 制造商:3m (tc) 系列:VHB?? 4910 零件状态:在售 底布，载体:丙烯酸泡棉 厚度 - 粘合剂:- 厚度 - 底布，载体:- 标准包装:1 |
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