User Manual

Interfacing and Controlling the RIM 801D Protocol support: Radio Access Protocol (RAP) 37
RIM 801D OEM Radio Modem – Integrator’s Guide
• A radio configured to operate in RAP mode can detect certain NCL
frames arriving on the serial port, and will automatically switch to
operating as an NCL radio.
The RIM Programmer’s Guide to RAP and SDU’s includes a complete
protocol specification and contains detailed information about RAP frames
and frame types. This information is summarized below.
RAP frame structure
An n-byte RAP frame has the following structure:
0 1 2 3456...n-6 n-5 n-4 n-3 n-2 n-1
Header Type Length Data Checksum Trailer
Figure 10: RAP Frame Structure
All parts of the RAP frame are necessary elements of the RAP
implementation.
The header consists of a unique sequence of values (0x9D, 0xAE, 0xBF).
This signals the beginning of a RAP frame to the RIM 801D radio modem.
The frame type indicates which one of the 18 different RAP frame types is
being used. The frame type determines the meaning of the data that is
enclosed in the RAP frame. These types are described in the next section.
Length indicates the number of bytes that are enclosed as data. This number
may be between 0 and 560.
Data is an optional field that encloses the data that is to be transmitted.
When transfering data, up to 560 bytes may be sent in each RAP frame.
RAP provides error-checking in the form of a checksum,asimple
summation of all the header, type, length,anddata bytes. Error-checking is
optional in RAP, but a RAP frame must always include a checksum field.
When error-checking is not used, the checksum bytes must be set to zero.
The frame ends with a trailer which, like the header, consists of a specific
sequence of values (0xFB, 0xEA, 0xD9). If the checksum received is
correct, then the trailer sequence can be ignored. If the radio receives a zero