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ELM329P 参数 Datasheet PDF下载

ELM329P图片预览
型号: ELM329P
PDF下载: 下载PDF文件 查看货源
内容描述: CAN解释 [CAN Interpreter]
分类和应用:
文件页数/大小: 76 页 / 353 K
品牌: ELM [ ELM ELECTRONICS ]
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ELM329  
Pin Descriptions  
MCLR (pin 1)  
A momentary (>2µsec) logic low applied to this input  
will reset the ELM329. If unused, this pin should be  
connected to a logic high (VDD) level.  
that has been set by PP 0C). If at a low level, the  
baud rate will always be 9600 bps.  
LFmode (pin 7)  
Vmeasure (pin 2)  
This input is used to select the default linefeed mode  
to be used after a power-up or system reset. If it is at  
a high level, then by default messages sent by the  
ELM329 will be terminated with both a carriage  
return and a linefeed character. If it is at a low level,  
lines will be terminated by a carriage return only.  
This behaviour can always be modified by issuing an  
AT L1 or AT L0 command.  
This analog input is used to measure a 0 to 5V  
signal that is applied to it. The value measured is  
scaled by a factor of about 5.7 and may be displayed  
using the AT RV command.  
Care must be taken to prevent the voltage from  
going outside of the supply levels of the ELM329, or  
damage may occur. If it is not used, this pin should  
be tied to either VDD or VSS.  
VSS (pin 8)  
Active LED (pin 3)  
Circuit common must be connected to this pin.  
This output pin is normally at a high level, and is  
driven to a low level when the ELM329 has  
determined that it has found a valid (active) protocol.  
The output is suitable for directly driving most LEDs  
through a current limiting resistor, or interfacing to  
other logic circuits. If unused, this pin may be left  
open-circuited.  
XT1 (pin 9) and XT2 (pin 10)  
A 4.000 MHz oscillator crystal is connected between  
these two pins. Loading capacitors as required by  
the crystal (typically 27pF each) will also need to be  
connected from each of these pins to circuit common  
(Vss).  
Note that the behaviour of this pin when the ELM329  
is in the low power mode may be modified by the  
logic level at pin 11, or with PP 0F, bit 4.  
When laying out a printed circuit board, you may  
wish to consider placing a guard ring around the  
oscillator crystal, pins, and capacitors, to provide a  
little isolation between them and the other signals  
(particularly the pin 11 CAN input).  
Control (pin 4)  
The level at this output may be directly controlled  
through AT commands. After any reset (powerup,  
AT Z, etc.), the output reverts to low level.  
Note that this device has not been configured for  
operation with an external oscillator, and it expects a  
crystal to be connected to these pins. Use of an  
external clock source is not recommended. Also,  
note that this oscillator is turned off when in the low  
power or ‘standby’ mode of operation.  
Pin 4 may also be used to provide an output signal  
that follows the internal CAN monitor output, by  
setting bit 0 of PP 0F to 1. This is a new feature with  
v2.0, and is not available with v1.0 ICs.  
CAN Monitor and A LED (pin 11)  
Memory (pin 5)  
This input serves two functions. If a CAN signal is  
detected at this pin, the ELM329 assumes that you  
wish it to monitor that signal, and possibly control the  
low power operation based on it.  
This input controls the default state of the memory  
option. If this pin is at a high level during power-up or  
reset, the memory function will be enabled by  
default. If it is at a low level, then the default will be  
to have it disabled. Memory can always be enabled  
or disabled with the AT M1 and AT M0 commands.  
If no CAN signal is detected, the ELM329 assumes  
that you are using this pin to control the behaviour of  
the Active LED output when the IC is in the low  
power mode (as it did for v1.0 ICs). In this mode, if  
pin 11 is at a high level when low power operation  
begins, the Active LED output will flash for about  
16 msec every 4 seconds. If the input is at a low  
level when low power operation begins, the  
Baud Rate (pin 6)  
This input controls the baud rate of the RS232  
interface. If it is at a high level during power-up or  
reset, the baud rate will be set to 38400 (or the rate  
3 of 76  
ELM329DSB  
Elm Electronics – Circuits for the Hobbyist  
www.elmelectronics.com