Specifications

© 2010 Cypress Solutions Complete Manual: CTM-15X Firmware 1.3.0
Open CTM (Revision D)
175
MODBUS Messages
Reg. #
Register content
Notes
0 – 5
Analog input 1 to 6 values
Value in volts x 100, big endian byte order
6
Modem supply Vcc
volts x 100, big endian byte order
7
Modem 1xRTT RSSI value
HEX, big endian byte order – units dBm (without the negative
sign)
8
Modem internal
temperature
HEX, big endian byte order – units degrees Celsius
9
GPS day & month
HEX
10
GPS year
HEX, big endian byte order
11
GPS hours & minutes
HEX
12
GPS seconds & GPS validity
flag
Seconds in HEX, Validity flag in ASCII: A = valid; V = invalid
13 – 14
GPS Latitude
Floating point radian format, little endian byte order. To
convert to degrees multiply by 180/pi (negative numbers are
South, positive are North)
15 – 16
GPS Longitude
Floating point radian format, little endian byte order. To
convert to degrees multiply by 180/pi (negative numbers are
West, positive are East)
17
GPS speed
Value in m/sec x 10
18
GPS heading
Value 0 to 359 degrees (integer)
11.5 Error response
If the modem is not able to correctly respond to a request then it will send an error response.
Error response format: 0xII 0x8N 0xXX 0xZZ 0xZZ
Where:
0xII is the modem’s assigned MODBUS ID
0x8N is the error code corresponding with the request:
0x81 is for read coils
0x82 is for read discrete inputs
0x84 is for read input registers
0x85 is for write coil
0xXX is the exception code: 0x01, 0x02, 0x03, or 0x04
0xZZ 0xZZ is the CRC checksum for this message
11.6 MODBUS TCP Messages
MODBUS TCP messages are identical to those used with standard MODBUS except that they drop the two
byte CRC check sum at the end of every message.