User's Manual

Page 56 of 83

A Carrier Corp. Company

PART NUMBER T82002163

REV A

timer. This timer is used as a count down timer that determines the timeout period for communications

between the monitor and host PC. Effectively what this means is that as long as this timer is refreshed

and not allowed to expire, communications mode will stay active allowing commands to be sent. The

monitor refreshes this timer any time valid command is sent, so as long as commands continue to be

sent, the monitor will continue to refresh the timer. If no commands are sent to the monitor within 3

minutes, communications mode within the monitor will be terminated. The reason for the 3-minute

timeout timer is to maximize the battery life of the monitor. Because of the power drain associated

with the communications mode, if the communications mode were allowed to continue indefinitely,

the battery would be drained very quickly.

Once the parameters or the 0h have been received, the monitor will then internally execute the command

and return a status byte followed by any additional data.

A status byte is always returned from the monitor upon completing a command whether or not there is any

additional data. The status byte is always a single byte value. A 0h value indicates successful

completion of the command while a non-zero value indicates an error. A list of valid status codes with

their names and descriptions are in the table below:

Status name Code Description

CMD_SUCCESSFUL 0x00 Returned upon successful completion of command.

CMD_UNKNOWN 0x02 The requested command is not part of the unit's API. This is returned

when a command does not exist.

PARAMETER ERROR 0x03 Parameter errors which are sent from the PC

BAD_TEMP 0x04 When an immediate temperature is requested, this value will be returned if

the conversion process did not complete successfully.

RESERVED (UNUSED) 0x05

BAD_INIT 0x07 The unit can not be initialized due to erroneous information having been

stored in its configuration pages.

UNIT_NEW 0x0A The unit is newly manufactured and un-configured.

UNIT_SLEEPING 0x0B The unit is sleeping prior to activation.

UNIT_SDELAY 0x0C The unit has been activated and is waiting through the startup delay.

UNIT_RUNNING 0x0D The unit has completed the startup delay and is actively recording data.

UNIT_STOPPED 0x0E The unit has been stopped after running.

Depending on the command that was sent, the monitor may or may not send data after the status code. For

instance, if the high-speed download command is sent to the monitor, the monitor will send all of the

temperature data after the status code has been sent.

The ULCM also supports a packet based command protocol which uses the same basic structure as the

ULCM standard commands with the exception that the command parameters and return data are in

packet form with a checksum attached. If the command has parameters then the host sends the

command parameter packet just after the monitor echoes back the command value. If the command

returns any data, then the monitor will return the data packet just after the status is sent. The

following figure illustrates this: