| 
| enum   | MODBUS_COMMANDS { T6713_COMMAND_RESET, 
T6713_COMMAND_STATUS, 
T6713_COMMAND_GET_FIRMWARE_REVISION, 
T6713_COMMAND_GET_GAS_PPM
 } | 
|   | 
| enum   | STATUS {  
  ERROR_CONDITION, 
FLASH_ERROR, 
CALIBRATION_ERROR, 
WARMUP_MODE, 
 
  SINGLE_POINT_CALIBRATION, 
RS232, 
I2C, 
RS485
 
 } | 
|   | 
| enum   | FUNCTION_CODES { READ_INPUT_REGISTERS = 4, 
WRITE_SINGLE_COIL, 
WRITE_SINGLE_HOLDING_REGISTER
 } | 
|   |