TMFirst Overview Group

The TMFirst API call finds the first multi-drop device on the 1-Wire network specified with the ‘session_handle’. A ROM search algorithm is used to find the first unique serial registration number (ROM) data pattern on the 1-Wire network. The ROM data pattern that was found is stored in an internal eight byte buffer. The internal eight byte buffer can be read using the TMRom API call.

short far pascal TMFirst(

long session_handle,    // session handle for the desired 1-Wire network
void far *state_buffer  // state buffer provided for the 1-Wire network session

For a description of the above types, see the TMEX Type Descriptions.



Specifies the session handle returned from the API function TMExtendedStartSession that specifies the desired 1-Wire network port. This parameter is required by most TMEX API functions.


Specifies a pointer to a memory location that TMEX keeps all of the state information for the 1-Wire networks. This parameter is required by most TMEX API functions.

Return Value

0 => device not found

1 => first device on the 1-Wire network found

<0 => TMEX Network Error Return Code

Code Example

See Also

TMNext, TMRom, TMFirstAlarm