SST Automation GT200-MT-CA, User Manual, Page: 25 / 31

User Manual
EtherNet to CAN Gateway
GT200-MT-CA
WWW.SSTCOMM.COM
25
If GT200-MT-CA received CAN frame on CAN network, the sequence number of input frame will add 1.
Users decide whether to use these CAN frame according to the needs.
b) Modbus TCP output register
Use function code 16 to write the data to Modbus output register of GT200-MT-CA, that is the CAN frame
needs to send.
The starting address is 0.
Every frame must include 8 register (16 bytes), or it will return Modbus exception response.
Byte 0 1 2 3 4-7 8-15
Meaning
Single/
Repeat
control
The data number
of CAN frame
Sequence
Number
Reserved
Frame header and
CAN frame mode
control
CAN frame
data
c) Bytes Definition
Byte 0 to 3 are controlling bytes
Byte 0: it indicates sending this sequence number of CAN frame once if it is zero, and it indicates sending
this sequence number of CAN frame periodically if it is non-zero, the cycle value is decided by this byte value:
period of transmission=the value of byte 0 * 10ms. For example, if the value of byte 0 is 10, the period of
transmission is 100ms, that is to say sending the frame one time every 100ms.
Byte 1: indicates the data number of CAN frame, the range is 0~8.
Byte 2: sequence number. The initial value of sequence number in output frame is non-zero (any value except
zero), if the mode is single transmission mode, the number must add 1 when sending a new frame, the gateway
will recognize that it is single transmission data, if the number reaches 255, the number will be 0 when adding 1.
CAN frame sequence number sends now must be different with the entire CAN frame sequence number sent last
time, or it won’t do any operation to current CAN frame.
Byte 4 to 7 are CAN frame header and CAN frame mode control (29 bit CAN ID). If the current CAN ID of
CAN frame is same with one in a cycle of transmission, the latter is removed, the current CAN is frame kept into
the buffer.
The format of byte 4 is as follow:
Bit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Meaning Reserved RTR Reserved The top five bits of frame header
Bit 6 of byte 4: RTR, 0 stands for data frame, 1 stands for remote frame.
Bit 0 to 4 of byte 4 to byte 7, CAN2.0A/2.0B frame header.
Byte 5:
Bit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Meaning The second high 8 bits of frame header
Byte 6:
Bit Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Meaning The second low 8 bits of frame header