Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Concentration Data Format Code
UUXXXYYY
UU
Unit
UU=00 ppm
UU=01 %LEL
UU=10 %V/V
UU=11 kppm
XXX
reserved
YYY
decimal place
YYY=000
no decimal places
YYY=001
1 decimal place
YYY=010
2 decimal places
YYY=011
3 decimal places
For example, (HEX) 81 (1000 0001) represents %V/V with 1 decimal place.
Concentration Example:
For a concentration value (HEX) 0062, 98 decimal, Format Code Interpretation:
0000 0000 (00)
98 ppm
1000 0001 (81)
9.8 %V/V
0100 0000 (40)
98 %LEL
Generic Responses
There are four generic responses. Each of these response packets is 6 bytes, and
contains the start byte, address, length, command code, ACK/NAK code and
Checksum. All ACK/NAK code is sent following the command code in the last
received packet.
ACK - 0x01
This is used for an acknowledgement of the handshake command.
NAK - 0x21
This is used for a negative acknowledgement of packet if the last received packet had
an incorrect checksum.
Bad Packet - 0x66
This is sent to the master when the start byte or length in the last received packet
is incorrect.
Unknown CMD –0x67
This response is sent by the slave when a command is not recognized.
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