Eaton ELC-PB, Programming Manual

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3 . I n s t r u c t i o n S e t
M N050 03003E F or mo re infor ma tio n vi sit:
w w w. e a t o n . c o m
3-235
COM Port I1
□0 interrupt
Special D
COM1 I140 D1167
COM2 I150 D1168
COM3 I160 D1169
10. Take standard MODBUS format for example:
ASCII mode
Field Name Descriptions
STX Start word = ‘: ’ (3AH)
Address Hi
Address Lo
Communication address:
The 8-bit address consists of 2 ASCII codes
Function Hi
Function Lo
Function code:
The 8-bit function code consists of 2 ASCII codes
DATA (n-1)
…….
DATA 0
Data content:
n × 8-bit data content consists of 2n ASCll codes
LRC CHK Hi
LRC CHK Lo
LRC check sum:
8-bit check sum consists of 2 ASCll code
END Hi
END Lo
End word:
END Hi = CR (0DH), END Lo = LF(0AH)
The communication protocol is in Modbus ASCII mode, i.e. every byte is composed of 2 ASCII
characters. For example, 64Hex is ‘64’ in ASCII, composed by ‘6’ (36Hex) and ‘4’ (34Hex). Every
character ‘0’…’9’, ‘A’…’F’ corresponds to an ASCII code.
Character ‘0’ ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’
ASCII code 30H 31H 32H 33H 34H 35H 36H 37H
Character ‘8’ ‘9’ ‘A’ ‘B’ ‘C’ ‘D’ ‘E’ ‘F’
ASCII code 38H 39H 41H 42H 43H 44H 45H 46H
Start word (STX): ‘:’ (3AH)
Address:
‘0’ ‘0’: Broadcasting to all drives (Broadcast)
‘0’ ‘1’: toward the drive at address 01
‘0’ ‘F’: toward the drive at address 15
‘1’ ‘0’: toward the drive at address 16
… and so on, max. address: 254 (‘FE’)
Function code:
‘0’ ‘3’: read contents from multiple registers
‘0’ ‘6’: write one word into a single register