User`s guide

Chapter 3 - Receiver Descriptions

inversion process in it. Most RS-232 driver/receiver integrated circuits (Maxim's MAX3232, for

example) will provide all these functions with only a +3V power supply.

Motorola Binary Format

NOTE: In the following discussion and in ensuing

areas of the manual concerned with communications

protocols, data characters without any prefixes will be

interpreted as decimal data, data beginning with ‘0x’

will be interpreted as hex data, and data beginning with

a lower case 'b' will be interpreted as binary data.

The native binary data messages used by all Oncore receivers (including the M12+) consist of a

variable number of binary characters (hex bytes). For ease of use, many Oncore users commonly

refer to these binary sequences by their ASCII equivalents. For instance, all binary messages

begin with the hex characters '0x40 0x40', which most users convert to the ASCII equivalents:

'@@'.

• The first two characters after the '@@' header comprise the Message ID and identify the

particular structure and format of the remaining data.

• This message data can vary from one byte to over 150 bytes, depending on the message

being transmitted or received.

• Immediately following the message data is a single byte checksum which is the

Exclusive-Or (XOR) of all bytes after the '@@' and before the checksum).

• The message is terminated with the Carriage Return/Line Feed pair: ‘0x0D 0x0A’.

Summarizing, every binary message has the following components:

Message Start:

@@ - (two hex 0x40's) denote the start of binary message.

Message ID:

(A.Z(a..z, A..Z) - Two ASCII characters - the first an ASCII upper-case letter, followed by

an ASCII lowercase or upper case letter. These two characters together identify the

message type and imply the correct message length and format.

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