Honeywell Touchpoint 4 - Time Diagram; Protocol Packet Definition; Packet Format; Start Code

Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Time diagram
Figure 1. Communication time diagram
Protocol Packet Denition
Packet Format
The format of packets using Touchpoint4 SERIAL COMMUNICATION PROTOCOL is as
follows:
Figure 2. Protocol packet format
Start Code Size:1byte.Always0x7F.
Slave Address Size: 1 byte.
Represents the Touchpoint4 gas detector controller address,
   0X01to0X10(1to16decimal).
Length Size: 1 byte.
The number of bytes in the Command field and Data field.
The total packet length is 4 bytes larger than this.
Command Size: 1 byte.
   Thisis0x30,0x40or0x41asdefinedintheremainderofthisbook.
Data  Size:0-250byte(s).
This section varies according to the chosen command and may
be omitted.
Checksum Size: 1 byte
   Thebit-wiseXORresultofallthepreviousbytesinthepacket.
   ThismakestheXORoftheentirepacket0X00.
Start
Code
Slave
Address
Length Command Data Checksum
5