Message Format And Example, Function 02 - GE 469 Communications Manual

MODBUS FUNCTIONS
Note
Note
6
Slave Response
Function Code
Byte Count
Bit Mask
CRC (low, high)
If a Starting Relay Coil (Starting Digital Input) of "0" is entered, the 469 will default it to "1". If
the Number of Relays (Number of Digital Inputs) requested exceeds the number of relays
available, the user is prompted with an

MESSAGE FORMAT AND EXAMPLE, FUNCTION 02:

The standard implementation requires the following: slave address (one byte), function
code (one byte), starting digital input (two byte), number of digital inputs to read (two
bytes), and CRC (two bytes). The slave response is the slave address (one byte), function
code (one byte), byte count of digital input mask (one byte), bit mask indicating the status
of requested digital inputs (one or two bytes), and CRC (two bytes).
The CRC is sent as a two byte number with the low order byte sent first.
Example 1: Request slave 11 to respond with status of digital inputs 5 to 9:
Digital Input
D1: Access
D2: Test
D3: Starter Status
D4: Emergency Restart
D5: Remote Reset
D6: Assignable Input 1
Master Transmission
Slave Address
Function Code
Starting Digital Input
Number of Digital Inputs
CRC (low, high)
Slave Response
Slave Address
Function Code
Byte Count
Bit Mask
CRC (low, high)
Example 2: Request slave 11 to respond with status of digital inputs 1 to 4:
Digital Input
D1: Access
D2: Test
Bytes Example
1 01
1 01
1 10
2 53 93
message.
ILLEGAL DATA
Status Digital Input
Closed D7: Assignable Input 2
Open D8: Assignable Input 3
Open D9: Assignable Input 4
Open Bit Mask (LSB)
Closed Bit Mask (MSB)
Closed
Bytes Example
1 0B
1 02
2 00 05
2 00 05
2 A8 A2
Bytes Example
1 0B
1 02
1 02
2 01 F0
2 C5 B9
Status Digital Input
Closed D6: Assignable Input 1
Open D7: Assignable Input 2
469 MOTOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE
COMMUNICATIONS GUIDE
Description
read relay coil status
1 byte bit mask
bit mask 0001 0000
computed CRC error code
Status
Closed
Closed
Closed
1111 0001
0000 0001
Description
message for slave 11
read digital input status
starting at digital input 5
5 digital inputs (inputs 5 to 9)
computed CRC error code
Description
message from slave 11
read digital input status
2 byte bit mask
bit mask of requested input
computed CRC error code
Status
Closed
Closed