Here is a brief description of what we decided to go along with for the ARCNET header. The NODE_ID filed is still the node id on each board. (If possible we will place them in a certain order). The FEMS software uses the reserved nodes (0xF0- 0xFF). The COMMAND field only has a few basic calls such as read and write. The DEVICE TYPE field will select the device being written or read to, such as a serial port, memory address or a data port. The data length is set by the control node and will be modified by the FEM when a read back is requested. If the ERROR field has a value other than zero, then an error or a reset has occurred at the FEM.

COMMAND WORD TABLE 1.

• The control node has to have a NODE_ID = 0x01.
• The NODE_ ID's = 0xF0 -- 0xFF are reserved.
• The COMMAND field must be placed at the beginning of the hopper memory.
• The GROUP COMMAND = 0x01 is reserved for a broadcast.
• The GROUP COMMAND = 0x00 is reserved for a single node transfer.
• The ERROR field must be set to 0x00 when the control node transmits data.
• The ERROR filed will return a value other than zero when an error occurs at a FEM. (data length = 0).
• The ERROR filed will be set to 0x01 when a node is reset for example NODE_ID = 5 & ERROR = 1 è node 5 was reset.
• The control node must be able to receive an ERROR PACKET from any FEM at any given point in time.