RS-232C Adjustment
7Check Sum
This is data to which
PC side
STX | ID | QUEST command | ETX |
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02 (hex) | 2 Byte | 3 Byte | 03 (hex) |
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Set side
STX | QUEST command | Data | Check sum | ETX |
02 (hex) | 3 Byte | *Byte | 2 Byte | 03 (hex) |
A detailed example is given below.
Example) The check sum value that is added when the QUEST command “QAA” returned the following
Data group (ASCII) | QUEST command | Data (6 Byte) | Check sum |
+ check sum | QAA | 100128 | xx (before calculation) |
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The data group is put into binary code one character at a time then displayed (only the last two digits are displayed).
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| 47 | 41 | 41 | 31 | 30 | 30 | 31 | 32 | 38 |
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When these values are added the result is 1F5 (hex).
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xx, where xx is 0B (hex), is added to 1F5 so the last two digits are 00 (in this case 200).
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As the data format, OB is converted to ASCII code and sent.
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The following data is output from the Plasma Display side.
STX | QUEST command | Data | Check sum | ETX |
02 (hex) | QAA | 100128 | 0B | 03 (hex) |
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*The returned data group is in capital letters. Please keep this in mind when introducing it into the binary display.
7Examples of check sum applications
Example 1) When the data is missing 1 Byte
STX | QUEST command |
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| Check sum | ETX | ||||
02 (hex) |
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| QAA |
| 100 (missing data) 28 |
| 0B | 03 (hex) | |||||
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| 47 | 41 | 31 | 30 | 30 | 32 | 38 |
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The data group is calculated according to rules by a PC application, and when these values are added the result is 1C4 (hex).
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A value xx, where xx is 3C (hex), is added to 1C4 such that the last two digits are 00 (in this case 200).
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Here, the check sum [OB (hex)] and the calculated [3C (hex)] do not match.
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Since they do not match, the PC application sends the QUEST command again and gets the data again.
Example 2) When 1 Byte of data in the data is unreadable
STX | QUEST command |
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| Data |
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| Check sum | ETX | ||||
02 (hex) |
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| QAA |
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| 100328 |
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| 0B | 03 (hex) | ||
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| 47 | 41 | 31 | 30 | 33 | 30 | 32 | 38 |
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The data group is calculated according to rules by a PC application, and when these values are added the result is 1F7 (hex).
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A value xx, where xx is 09 (hex), is added to 1F7 such that the last two digits are 00 (in this case 200).
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Here, the check sum [OB (hex)] and the calculated [09 (hex)] do not match.
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Since they do not match, the PC application sends the QUEST command | 19 |
again and gets the data again. |