Motorola M12 Oncore Guide de l'utilisateur télécharger pdf (Page 47)

Chapter 3 - Receiver Descriptions

Input/Output Processing Time

User commands sent to the M12+ are placed in an input buffer that is serviced once per second.

When powered on and available satellites are tracked, the current receiver position is available. If

insufficient satellite signals are received to develop a current fix, the last known position is output.

The message response time will be the time from the transmission of the first byte of input data to

the transmission of the last byte of output data. The command processing time will be skewed

since the time will be dependent on when the input message buffer is processed. For best case

processing, the input command would have to arrive just before the input buffer data is

processed, and the output response would have to be the first (or only) receiver output. For worst

case processing, the input command would have to arrive just after the input buffer data had

been processed, and the output response would have to be the last receiver output.

Assuming 1 ms per transmission of a data byte, assuming 50 ms command processing, and

assuming a uniform distribution for time of input command data entry, the best case, typical case,

and worst case scenarios are shown below.

Best Case UTC Time Correction command (@@Aw):

BC time = shortest command input + command processing + shortest command output

= 10 ms +50 ms +10 ms

= 70 ms

Typical Case UTC Time Correction command:

TC time = input anywhere across one second period + command processing + output anywhere

across one second period following command processing

= 0.5s+0.05s+0.475s

= 1.025 s

Worst Case UTC Time Correction command:

WC time = input beginning of one second period + output end of one second period

= 1 s+1 s

= 2 s

Note: The one command where these times are not applicable is the receiver's Self Test

command (@@Ia). The Self-Test command takes 5-10 seconds to complete.

Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05

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Motorola M12 Oncore Guide de l'utilisateur Page 47