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ELM624P 参数 Datasheet PDF下载

ELM624P图片预览
型号: ELM624P
PDF下载: 下载PDF文件 查看货源
内容描述: 控制L到RS232解释 [CONTROL L TO RS232 INTERPRETER]
分类和应用:
文件页数/大小: 7 页 / 47 K
品牌: ELM [ ELM ELECTRONICS ]
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ELM624  
ATE0 and ATE1  
default value is five (R5), and commands are  
always sent at least once (R0 is treated as R1).  
These commands control whether characters  
received on the RS232 port are retransmitted (or  
echoed) back to the host computer. To reduce  
traffic on the RS232 bus, users may wish to turn  
echoing off by issuing E0. Default is E1, echo on.  
ATI  
This causes the IC to identify itself. It simply sends  
the power-on string (for a version 1.0 IC, it is  
‘ELM624 v1.0 (c)1999’) and returns to the  
command mode.  
ATRn where ‘n’ is a Hex Digit  
This sets the LANC command repeat value.  
Although commands are only sent from the  
computer to the ELM624 once, they are sent on the  
Control L bus multiple times. While the Control L  
standard requires that commands must be repeated  
at least four successive times to be valid, the ATR  
command allows this parameter to be modified for  
experimentation or non-standard applications. The  
ATZ  
This combination causes the chip to perform a  
complete reset as if power were cycled off and then  
on again. All settings are returned to their default  
values.  
Data Transfer - The LANC Protocol  
Any valid four digit hex code that is received on  
the RS232 port will be converted to Control L format  
and transmitted out the LANC pin. The ELM624 makes  
no effort to determine whether the codes are valid or  
not. After sending the command, all responses  
received on the port are reported back to the RS232  
port using standard ASCII characters for the eight  
hexadecimal digits that represent the 4 bytes received.  
Note that control characters are not sent - the  
hexadecimal digit ‘A’ is transmitted as decimal value  
65, not 10.  
All transfers on the LANC bus occur at a rate  
determined by the device being controlled. The  
camcorder, or other device provides all of the timing or  
synchronizing pulses for the data transfer, and the  
ELM624 (in this case) must sense these sync pulses  
in order to send or receive data. If the controlled  
device is not providing these pulses for any reason, a  
‘NO SYNC’ error will result - check your cables and  
power supplies.  
a carriage return. The digits are combined in pairs to  
form the first two words to be sent on the Control L bus  
and, depending on the ATD option, may also be  
duplicated and sent on the interface as bytes 3 and 4.  
In the Control L standard, the first byte sent  
usually signifies the type of device being spoken to  
(eg. 1 for VTR and 2 for camera), as well as an  
identifying device number. These correspond to the  
first and second hex digits sent to the ELM624,  
respectively. The second byte (digits 3 and 4) is the  
actual command being sent. For example, the four  
character command string:  
1 0 3 4  
would normally be interpreted as ‘VTR #0 Play’, as the  
code for play is 34. Similarly, 1030 would stop the  
same VTR. Typical control codes follow:  
30 Stop  
36 Rewind  
32 Pause  
38 Fast Forward  
3A Record  
34 Play  
A Control L ‘data frame’ consists of 8 sequential  
bytes. Commands to the device (from the ELM624)  
are sent during the first half of the frame, while the  
second half (last four bytes) are for feedback from the  
controlled device. Often, four bytes are not enough to  
send all of the information, so data is multiplexed over  
several frames. An example of this is the time codes  
which contain information on days, hours, minutes and  
seconds which require several bytes to represent.  
The ELM624 does not send a command on the  
LANC bus until it has received four valid hex digits and  
8C Counter Reset  
The Control L device will respond with a sequence  
of 4 bytes (8 hex digits). The first byte (two digits) is  
always a status byte, having typical values as follows:  
02 Stopped  
03 Fast Forwarding  
06 Playing  
04 Recording  
72 Stopped - at tape beginning  
83 Rewinding  
The next nibble (third digit) is used to identify the  
ELM624DSB  
Elm Electronics – Circuits for the Hobbyist  
< http://www.elmelectronics.com/ >  
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