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In its current form, the board only takes instructions from the host terminal, and translates them into actions to perform. Each instruction has a four (4) byte header, of which the third and fourth byte are of most significance. The third byte is the control byte, which indicates what instruction to carry out. Table 1 contains a list of control bytes and the corresponding instructions which they will give to the board. The fourth byte of the header is the length of the payload, and can vary from 0 to 255. Upon the arrival of an instruction at the MCU, it is decoded and the relevant actions performed, such as changing the slot time, or sending a packet with or without the MAC-layer enabled.

Instruction Header Control byte Description
Instruction packet 0x11 Indicates that the incoming packet is an instruction packet. Any packets which are not preceded by this byte will be transmitted with the MAC sub-layer disabled.
Escaped byte 0x7D Indicates that the next byte was escaped, and needs to be un-escaped
New Packet 0x7E Resets the incoming buffer counter to receive a new packet
Transmit with MAC sub-layer enabled 0x10 Transmits the packet in the payload with the board's MAC sub-layer enabled. This handles retransmissions, ACKs and statistics collection. NOTE: The first byte of the instruction is used to denote the number of retries the MAC sub-layer will attempt.

Table: Table of Instruction Headers and associated bytes

Topic revision: r2 - 2012-08-16 - AhmetSekercioglu
 
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