Serial NO : S00206019-EN
Date of Editing : 2022-05-03
Questions : Why the protocol command can be executed correctly when the protocol command is directly sent to controller, but sometimes it succeeds and sometimes fails if sending the command through Listen Port of 701ServerSQL?
Answer：
This method is a specific command for mailbox, which is applied by the third software through 701Server Listen Port such as: Json, XML, Modbus, Enterprise E series controller communication protocol
Example introduction:
Please check whether the length of XOR and SUM check code is deducted when sending command through Listen Port of 701ServerSQL.
| Command Code | Description | |
| Head | 7E | 0x7 ( Fixed code) |
| Length | 06 | Data Length Indicator which denotes the length from Destination to the end including XOR and SUM(must less than 250 bytes) |
| DID | 01 | Destination Node ID 00: Reserved for the bus master FF: Broadcast to each reader |
| Command Code | 21 | Instruction Command |
| Data | 90 | Length of Data Block which varies depending on instructions |
| 03 | ||
| XOR | 4C | To XOR each byte from Destination ID to Data with 0xFF |
| SUM | 01 | TO sum each byte from Destination to XOR with 0x00. If the summary is greater than 0xFF, it should keep the low byte. |
For example: when the complete command packet to be sent to the controller is "7E 06 01 21 90 03 4C 01", the XOR & SUM check code of "4C 01" must be deducted, and the length 06 minus 2 becomes "04", Then send "7E 04 01 21 90 03" to controller through TCP Listen Port of 701Server will be correct.
More related resources:
► Access Controller- dual door
► INTEGRATION SOLUTIONS-Modbus