报头
No 代码 说明
--------------------------------------------------------
0 68 SD:(Start Delimiter)开始定界符(68H)
1 1B LE:(Length)报文数据长度
2 1B LER:(Repeated Length)重复数据长度
3 68 SD: (Start Delimiter)开始定界符(68H)
4 2 DA:(Destination Address)目标地址
5 0 SA:(Source Address)源地址
6 6C FC:(Function Code)功能码(读数据请求)
7 32 SDAP Byte; {32H}
8 1 SSAP {Req=01H, Rpl=03H}
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请求头
----------------------------------------------------
9 0 RQH_01_Word_0000
10 0
11 0 RQH_02_Word_0000
12 0
13 0 RQH_03_Word_DU_byte_count
14 E
15 0 RQH_04_Word_Extra_RH_bytes : Word;
16 0
17 4 RQH_05_Byte_Read_or_Write {Read=04H, Write=05H}
----------------------------------------------------------
数据单元
-------------------------------------------------
18 1 DQU_01_Word_120A
19 12
20 A DQU_02_Byte_10
21 10 DQU_03_Word_Nof_Requested_Bytes 22 2
23 0
24 1 DQU_04_Word_0000
25 0
26 1 DQU_05_Word_Register_Type
27 84 V=8400H V变量
28 0
29 3 地址为指针值,先取高位地址指针 (100*8) \ 256
30 20 取低位地址指针(100*8) Mod 256
-----------------------------------
结束
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31 8B FCS:(Frame Check Sequence)校验码
32 16 ED:(End
05-11-02 01:49