Installation manual Reader
25
Modifications, misprints and errors excepted
English
4.
Connections and displays
4.8.2.4.
Frame number
The frame number defines how many more frames there are in this data block. Only the first frame in a data block
can be shorter than 256 bytes. Each additional frame must have a length of 256 bytes (length byte LL is FF).
It is therefore possible to calculate the block size from the first frame number.
For example:
A block with 700 bytes of user data is to be transmitted. For this purpose the block is divided into three frames.
1. frame: 5A CD 50 02 – there now follow 200 bytes of user data – P1 P2
2. frame: 5A FF 50 01 – there now follow 250 bytes of user data – P1 P2
3. frame: 5A FF 50 00 – there now follow 250 bytes of user data – P1 P2
The receiver can use the frame number of the first frame (here 02) and its length byte to calculate the block size
(block size = frame number * 250 bytes + length byte -5) (here in the example: 2 * 250 bytes + 205 bytes - 5 bytes =
700 bytes), and reserve an appropriate amount of memory for the data.
4.8.2.5.
User data
User data are the bytes in a frame that flow into the block transmitted.
4.8.2.6. Checksum
The checksum is calculated using the polynomial x^16 + x^12 + x^5 + 1 with a pre-initialisation of 0x0000 from the
start code to the last user data byte.
4.8.3.
Network layer
As the KBRP is a point-to-point protocol, there is no network layer.
4.8.4.
Transport layer, session layer, presentation layer
Do not exist.
4.8.5.
Application layer
The application layer transmits data blocks from 1 to a maximum of 64000 bytes.
4.
Connections and displays
