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| 型號(hào)： | 4571 |
| 廠商： | Renesas Technology Corp. |
| 英文描述： | SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER |
| 中文描述： | 單芯片4位微機(jī)的CMOS |
| 文件頁(yè)數(shù)： | 85/126頁(yè) |
| 文件大小： | 1627K |
| 代理商： | 4571 |
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Rev.1.02
May 25, 2007
Page 61 of 124
REJ03B0179-0102
4571 Group
4. Oscillator concerns
Take care to prevent an oscillator that generates clocks for a
microcomputer operation from being affected by other signals.
(1) Keeping oscillator away from large current signal lines
Install a microcomputer (and especially an oscillator) as far as
possible from signal lines where a current larger than the
tolerance of current value flows.
<Reason>
In the system using a microcomputer, there are signal lines for
controlling motors, LEDs, and thermal heads or others. When a
large current flows through those signal lines, strong noise
occurs because of mutual inductance.
(2) Installing oscillator away from signal lines where potential
levels change frequently
Install an oscillator and a connecting pattern of an oscillator
away from signal lines where potential levels change frequently.
Also, do not cross such signal lines over the clock lines or the
signal lines which are sensitive to noise.
<Reason>
Signal lines where potential levels change frequently (such as the
CNTR pin signal line) may affect other lines at signal rising edge
or falling edge. If such lines cross over a clock line, clock
waveforms may be deformed, which causes a microcomputer
failure or a program runaway.
Fig 67. Wiring for a large current signal line
Fig 68. Wiring to a signal line where potential levels
change frequently
(3) Oscillator protection using VSS pattern
As for a two-sided printed circuit board, print a VSS pattern on
the underside (soldering side) of the position (on the component
side) where an oscillator is mounted.
Connect the VSS pattern to the microcomputer VSS pin with the
shortest possible wiring. Besides, separate this VSS pattern from
other VSS patterns.
Fig 69. Vss pattern on the underside of an oscillator
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 or an I/O port, since the output data may
reverse because of noise, rewrite data to its port latch at fixed
periods.
Rewrite data to pull-up control registers at fixed periods.
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 operation, 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
multiple times in a single main routine processing.
XIN
XOUT
VSS
M
Microcomputer
Mutual inductance
Large
current
GND
XIN
XOUT
VSS
CNTR
Do not cross
N.G.
Oscillator wiring
pattern example
An example of VSS patterns on the
underside of a printed circuit board
Separate the VSS line for oscillation from other VSS lines
XIN
XOUT
VSS
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 45722.123.242 | 1 mm2, COPPER ALLOY, WIRE TERMINAL |
| 45733.201.004 | 2.5 mm2, COPPER ALLOY, WIRE TERMINAL |
| 45733.417.031 | 2.5 mm2, WIRE TERMINAL |
| 45744.123.211 | 6 mm2, COPPER ALLOY, WIRE TERMINAL |
| 45744.201.004 | 6 mm2, COPPER ALLOY, WIRE TERMINAL |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 4571_08 | 制造商:RENESAS 制造商全稱(chēng):Renesas Technology Corp 功能描述:Standard Characteristics |
| 45-710 | 制造商:GC Electronics 功能描述:EXTENSION CABLE, PARALLEL, 6FT, PUTTY; Cable Length - Imperial:6ft; Cable Length - Metric:1.83m; Connector Type A:Centronics 36 Position Plug; Connector Type B:Centronics 36 Position Receptacle; Jacket Color:Putty; Cable Color:Putty 制造商:Calrad Electronics 功能描述:Cable Assembly Parallel 6m 28AWG 36 POS SCSI to 36 POS SCSI M-F |
| 4-571011-3 | 功能描述:ANVIL 制造商:te connectivity amp connectors 系列:* 零件狀態(tài):有效 標(biāo)準(zhǔn)包裝:1 |
| 457102-1 | 制造商:TE Connectivity 功能描述:BLOCK, PLATE MTG - Bulk |
| 45710224PTC2103 | 制造商:Omron Corporation 功能描述: |
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