User's Manual

Page 68 of 83

A Carrier Corp. Company

PART NUMBER T82002163

REV A

The command parameter packet and data packet use the same packet format, which is

shown below:

Packet

Packet Data Checksum

3 byte count of the number of

parameters or data bytes to

Parameter or Data bytes

B0 B1 B2 D0, D1, D2, D3, ……….Dn 1Byte

For instance if a Omega TT4 command to download all the data is sent to the monitor,

the monitor will send (after the status byte) a packet containing a 3-byte value

representing the number of data bytes to follow, the data (which includes summary

information and temperature data), and a checksum.

For any packet, the checksum is the least significant byte of the sum of all the data in the

packet including the 3-byte count. This is shown in the example below:

If the packet contains 1120 data bytes and the value of

all the bytes is a hex 76 then the sum of the count bytes

and data bytes is as follows:

Count Byte 0 0x60

Count Byte 1 0x04

Count Byte 2 0x00

460H

(1120D)

Data Byte 0 0x76

Data Byte 1 0x76

Data Byte 2 0x76

. .

Data Byte 1119 0x76

Data Byte 1120 0x76

Data

Packet Data

Sum equals  0x208A0

Sum

Once the sum has been calculated, only the least

significant byte, in this case 0xA0, is used as the

checksum.