Rockwell Automation 900 Temperature Controller Communications Functions - Series B - Manual (Page 17)

2-1 Publication 900-UM004D-EN-E - July 2010
Chapter
2
Bulletin 900 Communications Procedures
900-TCx (CompoWay/F)
Data Format Unless otherwise indicated, numbers in this manual are expressed in
hexadecimal (with an H’ before the number: e.g., H’02). Values without the H’,
such as 00, are ASCII. The number underneath each delimiter in a frame
indicates the number of bytes.
Command Frame
BCC Calculation Example
The BCC (Block Check Character) is determined by calculating the exclusive
OR of the bytes from the node number up to ETX. The 8-bit result is written
to the BCC byte at the end of the frame.
Table 2.1
STX This code (H’02) indicates the beginning of the communications frame
(text). Always set this character in the first byte. When STX is received
again during reception, reception is carried out again from the point
where STX was received.
Node number • This number specifies the transmission’s destination.
• Specify the 900-TCx’s communication unit number.
• A BCD value between 00 and 99 or an ASCII value of XX can be set.
• Specify XX for a broadcast transmission. No responses will be
returned for broadcast transmissions.
• No responses will be returned from node numbers other than the
ones in the above range.
Sub-address This is not used on the 900-TCx . Be sure to set the sub-address to 00.
SID (service ID) This is not used on the 900-TCx . Be sure to set the Service ID to 00.
Command text Command text area. Refer to Structure of Command Text on page 2-5
ETX This code (H’03) indicates the end of the text.
BCC Block Check Character The BCC result is found by calculating the
exclusive OR of the bytes from the node number up to ETX.
STX
Node No.
1 2 2
Sub-address
0 0 0
SID
1
BCC Calculation Range
Text
Command Text
ETX
BCC
1 1
STX Node No. Sub-address SID Command Text ETX BCC
02H 0(30H) 0(30H) 0(30H) 0(30H) 0(30H) 0(30H) 5(35H) 0(30H) 3(33H) 03H 35H
BCC=30H
⊕
30H
⊕
30H
⊕
30H
⊕
30H
⊕
30H
⊕
35H
⊕
30H
⊕
33H
⊕
03H=35H
Calculation result 35H is set to the BCC area.
The
⊕
symbol indicates exclusive OR operation and the H indicates hexidecimal code.