Trimble Outdoors Part Number 45005-00-ENG, AcutimeTM2000 Synchronization Kit Packet Structure

Trimble Standard Interface Protocol A

meaning and format of the data that follows. Each packet begins and ends with control characters.

A.1.1 Packet Structure

TSIP packet structure is the same for both commands and reports.The packet format is:

<DLE> <id> <data string bytes> <DLE> <ETX>

<DLE> is the byte 0x10, <ETX> is the byte 0x03, and <id> is apacket identifier byte, which can have any value except for <ETX>and <DLE>. The bytes in the data string can have any value. To prevent confusion with the frame sequences <DLE> <id> and <DLE><ETX>, every <DLE> byte in the data string is preceded by an extra<DLE> byte ('stuffing'). These extra <DLE> bytes must be added ('stuffed') before sending a packet, and removed ('unstuffed') after receiving the packet.

!Note – A simple <DLE> <ETX> sequence does not necessarily signify the end of the packet, as these can be bytes in the middle of a data string.The end of a packet is <ETX> preceded by an odd number of <DLE> bytes.

Multiple-byte numbers (integer, float, and double) follow the ANSI/ IEEE Std 754 IEEE Standard for Binary Floating-Point Arithmetic as illustrated below. They are sent most-significant-byte-first. This may involve switching the order of the bytes as they are normally stored in Intel-based machines. Only the fractional part of the mantissa for real numbers, SINGLE and DOUBLE, is reported because the leading bit on the mantissa is always 1. Specifically:

INTEGER is a 16-bit unsigned number sent in two's complement format.

SINGLE (float, or 4 byte REAL) is sent as a series of four bytes; it has a precision of 24 significant bits, approximately 6.5 digits.

A-2 Acutime 2000 Synchronization Kit User Guide