CHAPTER 4
COMMUNICATION PROTOCOLS
4-5
DC-20 and DC-21 operation manual
To write values in the display, the following message must be sent:
Addr.
Func.
Register
High
Register
Low
Words
High
Words
Low
Num.
bytes
10h
01h
01h
0
5
0Ah
03h
10h
01h
01h
00h
05h
09h
Data
L
OW
CRC
High CRC
V T
25,3
47
56h 54h
32h 35h 2Ch 33h
20h
34h 37h
00h
F4h
9Ch
The first byte is the address of the display inside the network. The three following bytes
must be 10h, 01h and 01h. The bytes 5 and 6 correspond to the number of words of the data
field. In the data field the characters “VT” must be placed, followed by the temperature and
humidity data. At the end, a 00h character must be sent so the number of byte sent is even.
The response from the display is the following message:
Addr. Func.
Register
High
Register
Low
Words
High
Words
Low
Num.
bytes
Data
Low
CRC
High
CRC
10h
01h
01h
00h
01h
02h
V T
03h
10h
01h
01h
00h
01h
02h
56h 54h
90h
7Eh
In the response message, the received code is repeated until the control code (V). If the
display detects an error in the received block, the error code with the following data code is sent
Addr.
Error
Error code
Low CRC
High CRC
90h
The possible errors are:
02 = CRC error.
