Rockwell Automation 900 Temperature Controller Communications Functions - Series B - Manual (Page 10)

Publication 900-UM004D-EN-E - July 2010
1-2 About Communications Methods
Communications
Specifications
Note: Highlighted characters in the table above indicate defaults.
➊ Direct RS-232C communication is only available with the 900-TC8. However, the 900-CONVx25(B) RS232/USB
to RS485 converter can be used for 900-TC16 and 900-TC32 controllers.
➋ Communications speed, data bits, stop bits and vertical parity can each be configured independently in the
controller’s Communications Setting function group.
➌ 900-TC8, 900-TC16, and 900-TC32 Series B controllers only.
➍ The communications data length for Modbus must be 8 bits.
Transmission procedure When the host device transmits a command frame, the 900-TCx transmits a
response frame that corresponds to the command frame. A single response
frame is returned for each command frame. The following diagram shows the
operation of the command and response frames.
Allow a wait time of at least 2 ms until the next command is sent after the host
device receives a response from the 900-TCx temperature controller.
Table 1.1
Transmission line connection➊ RS-485 : Multiple point, or RS-232C : Point to point
Communications method➊ RS-485 (2-wire, half-duplex), or RS-232C
Synchronization method Start-stop synchronization
Baud rate 1200, 2400, 4800, 9600 , 19200, 38400, or 57600 bps
Communication code➋ ASCII
Data bits➋ 7 or 8 bits
Stop bits➋ 1 or 2 bits
Error detection
−
Parity (none, even or odd) BCC (block check
character)
−
BCC with CompoWay/F (900-TC)
−
CRC-16 (Cyclic Redundancy Check 16) Modbus➍
communications
Flow control None
Interface➊ RS-485/RS-232C
Retry function None
Communications buffer 217 bytes➌, 40 byte
Communications response wait
time 0 to 99 ms, default time: 20 ms
Host Device
900-TCx Temperature Controller
Command Frame Command Frame
Response Frame